<p class="jove_content" style=";text-align:right;direction:rtl"> وأيد هذا العمل من المنح المقدمة من SNF [31003A-138528]، وOctav ومؤسسة مارسيلا Botnar، مؤسسة نوفارتيس ومؤسسة إيما Muschamp. نشكر مارتين Lambelet، وجان كريستوف Stehle للمساعدة التقنية الممتازة. </p>

<p class="jove_content" style=";text-align:right;direction:rtl"> وافقت اللجنة الأخلاقية من جامعة لوزان التجارب، والتي هي وفقا للمبادئ الواردة في إعلان هلسنكي لعام 1975، بصيغته المنقحة في عام 1983 لاستخدام الأنسجة البشرية. </p><p class="jove_title" style=";text-align:right;direction:rtl"> 1. الإنسان العظمى الوريد الصافن الحصاد </p><ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> الحصول على شرائح الفائض من غير دوالي الأوردة الصافن الإنسان من المرضى الذين يخضعون لجراحة الأطراف السفلية الالتفافية لنقص التروية. في غرفة العمليات، وتطهير المحطة بالكامل مع محلول اليود وثنى المريض لفضح الساق من الفخذ إلى القدم. </li><li style=";text-align:right;direction:rtl"> إجراء شق متوسط ​​من الفخذ إلى الركبة (ترك الجزء الجلد توقف). </li><li style=";text-align:right;direction:rtl"> حصاد الوريد الصافن الكبير مع عنيق المحيطة (تقنية عدم اللمس) الأنسجة. فروع جانبية آمنة الأوردة 4-0 العلاقات مع الحرير. تخزين على الفور ما لا يقل عن 9 سم شريحة فائض طويلة من الوريد الصافن أكبر، مع القطر الخارجي من 2.5-4 ملم في 4 درجات مئوية في RPMI-1640 Glutamax المتوسطة، تستكمل مع 12.5٪ مصل العجل الجنين وجعله إلى المختبر. </li></ol><p class="jove_title" style=";text-align:right;direction:rtl"> 2. EVPS التصميم </p><ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> تجميع المعدات العامة هو مبين في <strong>الشكل 1.</strong> الأوتوكلاف جميع المعدات والحفاظ على جميع مكونات تحت ظروف معقمة. وبالإضافة إلى ذلك، تأكد من أن النظام هو ماء ولا تسرب المواد الكيميائية في المتوسط. استخدام الميثيل polymethacrylate (PMMA-GS) للتغطية. الصلب (X5 كر ني 18 10) والبلاستيك polyoxymethylene (بوم) والدعم الوريد. </li><li style=";text-align:right;direction:rtl"> تصميم غرفة نضح لهندسة المطلوب للسماح موضع الوريد وعلاقته. تأكد من عمق (أو نصف القطر في حالة استخدام بناء أسطواني) هو 2.5 سم على الأقل لذلك يسمح الحد الأدنى من انثناء وتمدد السفينة جنبا إلى جنب مع تغطية مستمرة من قبل وسائل الإعلام ثقافة <strong>(الشكل 1).</strong> الختم هو قضية رئيسية والسبب يستخدم مستطيل البناء PMMA-GS. </li><li style=";text-align:right;direction:rtl"> تصميم الدعم الوريد إلى geometr المطلوبذ. لتجنب مجعد الوريد أو عبر انتفاخ، والسماح تعديل طول طريق دفع أو سحب (المسمار لا يمكن أن تستخدم لهذا الغرض، كما الوريد سوف تكون ملتوية مع المسمار). <br /> ويستخدم قضيب من الصلب الكامل متصلة بواسطة 2 انزلاق على شكل L القطع التي تدعم اسطوانات الوريد (2 5 مم لتناسب السفينة) والوريد <strong>(1B الشكل والشكل 2)</strong> هنا: ملاحظة. </li><li style=";text-align:right;direction:rtl"> تصميم عمود الضغط، بحيث يكون &quot;الضغط يستريح&quot; المطبقة على هذا النظام هو: ع = 0-10 = HX ρ x ج، حيث p = الضغط (N / م <sup>2،</sup> باسكال) ح = ارتفاع عمود السائل (م) ρ = كثافة السائل (كجم / م <sup>3)</sup> و (ز) = ثابت الجاذبية (9.81 متر / ثانية <sup>2).</sup> تصميم أربع قنوات اتصال، من أعلى إلى أسفل: لتطبيق الضغط، للخروج (من الوريد)، تدفق (إلى الوريد) والسماح التغيير المتوسط. </li><li style=";text-align:right;direction:rtl"> إعداد المتوسطة. استنادا إلى الدراسات السابقة <sup>5،11-14،</sup> اختر RPMI-1640، على أن تستكمل مع Glutamax، 12.5٪ مصل العجل الجنين، و 1٪ حل للمضادات الحيوية مضاد فطري (10،000 U / مل البنسلين G، بالإضافة إلى 10 ملغ / مل كبريتات الستربتومايسين، بالإضافة إلى 25 ملغ / مل الأمفوتريسين B، بالإضافة إلى 0.5 ميكروغرام / مل: الجنتاميسين). وتعطى إجهاد القص (SS) بواسطة SS = 4 μQ / π * ص <sup>3</sup> س هو معدل التدفق (مل / ثانية)، ص نصف قطرها (سم) من الجزء الوريد، وμ هي اللزوجة من المتوسط ​​الارواء. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> SS تعدل عن طريق ضبط اللزوجة من خلال إضافة 70 كيلو دالتون ديكستران. قياس اللزوجة مع مقياس اللزوجة. هنا، إضافة 8٪ 70 كيلو دالتون ديكستران لوضع SS إلى 9-15 داين / سم <sup>2.</sup> </li></ol></li><li style=";text-align:right;direction:rtl"> ضبط مضخة تستعد للحث على إشارة قلبي الشكل نابض من 60 نبضة / دقيقة والسعة ثابتة توليد تدفق أحادي الاتجاه من 150 ± 15 مل / دقيقة، مستقلة عن الضغوط التي مورست في النظام والتي يسيطر عليها جهاز كمبيوتر. تأكد من أن برنامج القيادة يدمج الاستحواذ المستمر ورصد الضغوط، سرعة تدفق، ومعدل النبض، وإشارة. إذا رغبت في ذلك، استخدام مضخة الثانية (غير متزامنةhronized) لإنتاج غير الصفحي، التدفق المضطرب. </li></ol><p class="jove_title" style=";text-align:right;direction:rtl"> 3. الجمعية EVPS (الشكل 1) </p><ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> قبل البدء، تأكد من أن جميع المعدات معقمة. تنفيذ كافة الخطوات التالية في عقامة تحت غطاء تدفق الصفحي. </li><li style=";text-align:right;direction:rtl"> وضع الوريد في طبق بيتري مليئة متوسطة. استخدام شفرة جراحية وتقسيم العرق إلى 3 شرائح متساوية. </li><li style=";text-align:right;direction:rtl"> شطف على الفور شريحة واحدة في برنامج تلفزيوني. تقسيم قطعة في 3 أجزاء، وتحديد واحد في الفورمالين لقياس الأشكال. تجميد اثنين آخرين للحصول على النسخة الكمي (RT-PCR) والبروتين (وصمة عار الغربية) التحليل. النظر في هذه القطاعات كعنصر تحكم، الوريد غير perfused ل. </li><li style=";text-align:right;direction:rtl"> استخدام شرائح 2 المتبقية لنضح. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> حقن بلطف شديد المتوسطة في الوريد وتحديد اتجاه التدفق العادي؛ في وجود صمامات يتم عكس الوريد. </li><li style=";text-align:right;direction:rtl"> اغلاق الأوردة هو من أهمية قصوى لنجاح التجربة. تحقق من وجود تسرب من خلال الضمانات. تأمين أي تسرب مع خيوط الحرير 6-0. </li> &lt;/ OL&gt; </li><li style=";text-align:right;direction:rtl"> ربط قطاع الوريد بين اثنين من الاسطوانات المعدنية، نهاية واحدة في وقت واحد (2.3، <strong>الشكل 1).</strong> تأمين اسطوانات مع Ethibon 3-0 حول الفجوات <strong>(الشكل 1A و B).</strong> <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> وضع شريحة الوريدي بأكمله في غرفة نضح شغل سابقا مع المتوسط. كرر نفس الإجراء الجزء الثاني. <br /> ملاحظة: إن الفشل في اغلاق الوريد بشكل صحيح إلى اسطوانة تكون مصدرا للتسرب، تتطلب إعادة التداخل، وزيادة كبيرة في خطر العدوى والفشل التجريبية. </li></ol></li><li style=";text-align:right;direction:rtl"> لتعزيز (شبكة) الجزء الثاني، والإفراج عن اثنين من اسطوانات (مع الوريد المرفقة) من على شكل L قطعة (2.3) <strong>والشكل (1).</strong> <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> أن يكون لطيف و لا تلمس الوريد مع أي الصكوك. حرك شبكة أولا على اسطوانة ثم الى الوريد. وهناك التدافع دفع / سحب حصول على عيون في الوريد. </li><li style=";text-align:right;direction:rtl"> مرة واحدة تغطي شبكة كامل سطح الوريد تأمين يacketed الوريد إلى اسطوانات مع Ethibon 3-0. </li><li style=";text-align:right;direction:rtl"> يحشدوا مجمع الوريد / اسطوانة للدعم على شكل L وتحويلها إلى غرفة نضح، وشغل سابقا مع المتوسط. </li></ol></li><li style=";text-align:right;direction:rtl"> ربط كل اسطوانة معدنية (في وتدفق) إلى Y-الخائن باستخدام المعالجة بيروكسيد أنابيب السيليكون مع قطرها الداخلي 3.2 مم. </li><li style=";text-align:right;direction:rtl"> ربط الخائن تدفق إلى الثاني Y-الخائن باستخدام نفس النوع من الأنابيب. من هذا Y-الخائن، استخدام أنبوب واحد لقياس ضغط التروية من خلال كل السفن. ربط الآخر إلى العمود لتشكيل نظام حلقة مغلقة <strong>(الشكل 2).</strong> </li><li style=";text-align:right;direction:rtl"> داخل الحاضنة، واستخدام طويل (متر واحد طول) أنبوب لتوصيل عمود الضغط في الرأس مضخة. </li><li style=";text-align:right;direction:rtl"> استكمال إنشاء طريق ربط رئيس المضخة إلى تدفق Y-الخائن مع طول أنبوب طويل آخر <strong>(الشكل 1).</strong> </li></ol><p class="jove_title" style=";text-align:right;direction:rtl"> 4. الأوردة الإرواء </p><ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> بعد أن كانت الجمعية EVPS التعاونmpleted، وملء العمود مع المتوسطة (البقاء تحت لاصق الوريد تدفق للسماح إعادة تعبئة). إضافة المزيد من المتوسطة إلى العمود حتى النظام ممتلئ. نقل كافة النظام في الحاضنة الحفاظ على 37 ± 0.1 درجة مئوية مع درجة الحموضة أبقى ثابتا عند 7.40 ± 0.01 (باستخدام خوارزمية CO <sub>2</sub> / درجة الحموضة على أساس معادلة هندرسون-Hasselbach). </li><li style=";text-align:right;direction:rtl"> جلب رئيس مضخة والعتاد خارج الحاضنة وتوصيله إلى محرك مضخة والعتاد. المسمار قضبان لتأمين التجمع. </li><li style=";text-align:right;direction:rtl"> تبديل على السلطة مضخة، تأكد من تفعيلها على برنامج القيادة والسماح 5 دقائق على المدى المتوسط ​​ليتم توزيعها بالتساوي في كل حجرة. </li><li style=";text-align:right;direction:rtl"> لمراقبة الضغط، استخدام خط المراقبة الشرياني. وصل الناتج الضغط EVPS (أنه يتوافق مع القسطرة الشريانية) إلى محول الضغط مرتبطة بالكمبيوتر. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> تأكد شغل في الأنبوب تماما مع المتوسطة ولا يحتوي على أي فقاعات. دي فقاعة نظام الثقافة من خلال &quot;لي الشريانيشمال شرق &quot;أنبوب <strong>(الشكل 2).</strong> إيلاء الاهتمام لعرض والبحث عن إشارة قلبي الشكل نابض من 60 نبضة / دقيقة السعة ثابتة. عند هذه النقطة، والضغط المتوسط ​​هو بين 0-10 ملم زئبق. إذا كان الضغط &lt;0 والعمود يفرغ تدريجيا نبحث عن تسرب (ضمانات الوريد أو عدم كفاية ختم بين الوريد وأنبوب). </li></ol></li><li style=";text-align:right;direction:rtl"> ضبط ضغط الحد الأدنى إلى 6 ملم زئبق لاختبار الوريدي أو على 90 ملم زئبق للاختبار الشرياني. في ظل هذه الظروف، حاقن الهواء ينطبق الضغط المطلوبة لعمود والنظام. </li><li style=";text-align:right;direction:rtl"> تغيير المتوسطة كل أيام 2 باستخدام الأنبوب متصلا عمود الضغط. لمنع الضرر التغير في الضغط، افتح المكونات العمود أولا. </li></ol><p class="jove_title" style=";text-align:right;direction:rtl"> 5. الانتهاء من الإرواء </p><ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> بعد 3 أو 7 أيام من نضح: اتخاذ EVPS من الحاضنة وترجل الأوردة. تجاهل 5 مم الداني والقاصي ينتهي المرفقة الوريد إلى المعدات. خفض المركزي، رين 5 ممع من قطاع المتبقية وإصلاح في الفورمالين (قياس الأشكال). تجميد الأجزاء المتبقية والحد إلى مسحوق لمزيد من التحليلات الجزيئية. </li></ol>

<ol>
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Recherches Chirurgicales Europeennes</em>. <b>45</b>, 50-59 (2010).</li><li>Dubuis, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atorvastatin-loaded+hydrogel+affects+the+smooth+muscle+cells+of+human+veins.">Atorvastatin-loaded hydrogel affects the smooth muscle cells of human veins.</a> <em style='font-style: italic'>The Journal of pharmacology and experimental</em>. <b>347</b>, 574-581 (2013).</li><li>Deglise, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+connexin43+expression+in+human+saphenous+veins+in+culture+is+associated+with+intimal+hyperplasia.">Increased connexin43 expression in human saphenous veins in culture is associated with intimal hyperplasia.</a> <em style='font-style: italic'>Journal of Vascular Surgery</em>. <b>41</b>, 1043-1052 (2005).</li><li>Muto, A., Model, L., Ziegler, K., Eghbalieh, S. D., Dardik, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+vein+graft+adaptation+to+the+arterial+circulation:+insights+into+the+neointimal+algorithm+and+management+strategies.">Mechanisms of vein graft adaptation to the arterial circulation: insights into the neointimal algorithm and management strategies.</a> <em style='font-style: italic'>Circulation Journal : Official Journal of the Japanese Circulation Society</em>. <b>74</b>, 1501-1512 (2010).</li><li>Tao, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simplified+murine+intimal+hyperplasia+model+founded+on+a+focal+carotid+stenosis.">A simplified murine intimal hyperplasia model founded on a focal carotid stenosis.</a> <em style='font-style: italic'>The American Journal of Pathology</em>. <b>182</b>, 277-287 (2013).</li><li>Berard, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Salvage+treatment+for+venous+aneurysm+complicating+vascular+access+arteriovenous+fistula:+use+of+an+exoprosthesis+to+reinforce+the+vein+after+aneurysmorrhaphy.">Salvage treatment for venous aneurysm complicating vascular access arteriovenous fistula: use of an exoprosthesis to reinforce the vein after aneurysmorrhaphy.</a> <em style='font-style: italic'>European Journal of Vascular and Endovascular Surgery : the Official Journal of the European Society for Vascular Surgery</em>. <b>40</b>, 100-106 (2010).</li></ol>

<p class="jove_content" style=";text-align:right;direction:rtl"> الكتاب ليس لديهم ما يكشف. </p>

<p class="jove_content" style=";text-align:right;direction:rtl"> تكشف هذه الدراسة <em>المجراة سابقا</em> نظام الوريد نضح (EVPS) لإجراء دراسات واسعة في الدورة الدموية عروق الإنسان. هذا النظام يسمح الأوردة الصافن نضح تحت معلمات الدورة الدموية محددة في غياب العوامل الالتهابية والنمو المشددة الصادرة عن تعميم الخلايا <em>في الجسم الحي.</em> وبا...

<p class="jove_content" style=";text-align:right;direction:rtl"> أمراض القلب والأوعية الدموية هي السبب الرئيسي للمراضة والوفيات في الدول الغربية <sup>1.</sup> على الرغم من التقدم المحرز في العلاجات اللف، تبقى عملية جراحية في العمود الفقري العلاجات المعاصرة، تتم الآن أكثر من نصف مليون ترقيع الوريد سنويا في الولايات المتحدة. ومع ذلك، على الرغم من عقود من البحث، 30-60٪ أقل من الطعوم أقصى الوريد تفشل في غضون السنوات الأولى بسبب تضخم باطنة (IH) <sup>2.</sup> القوات الميكانيكية، والإجهاد المنخفض بشكل خاص القص (SS) والتوتر الشديد الجدار، تقوم بدور محوري في بدء وتطوير هذه الاستجابة المفرطة التصنع <sup>3،4.</sup> لمعالجة هذه القضية، تم إنشاؤها <em>بحكم فيفو</em> الأوردة نظام نضح (EVPS) للدراسة، في ظل ظروف رقابة صارمة الدورة الدموية (ضغط وإجهاد القص)، وسلوك الصافن عروق الإنسان. في هذه الدراسة، بعد الإدراج إلى الدورة الدموية مثل الشرايين، وارتفاع ضغط (يعني = 100 ملم زئبق) كان كافيا لتحفيز proliferation والهجرة من خلايا العضلات الملساء في طبقة باطنة (IH) <sup>5.</sup> </p><p class="jove_content" style=";text-align:right;direction:rtl"> واشارت دراسات الثدييات استخدام التعزيز الخارجي وسيلة فعالة لدعم &quot;ريد arterialized&quot; ومواجهة التغيرات في الدورة الدموية الحادة الوريد يواجه مزروع مرة واحدة إلى الوسط الشرياني. شبكة منعت الإفراط في انتفاخ، زيادة إجهاد القص، وخفض التوتر الجدار وبالتالي IH <sup>6-10.</sup> ومع ذلك، فإن الآليات الكامنة وانطباقها على عروق الإنسان في تحسين الالتفافية المباح لم يتميز بشكل كامل. تم استخدام EVPS جهدنا لمقارنة، في حالة محاكاة التعديلات الوريد تواجه إدراج مرة واحدة إلى نظام الشرياني (إجهاد القص العالية والضغط)، وسلوك الإنسان الأوردة الصافن في غياب وجود macroporous شبكة البوليستر أنبوبي الخارجية. عن طريق منع إعادة عرض المرضية وIH، قدمت شبكة دليل على فعاليته المحتملة السريرية <sup>11</sup> </sup&gt;. </p><p class="jove_content" style=";text-align:right;direction:rtl"> هذه الدراسة 1) يقدم نموذجا <em>للخارج الحي</em> الصافن عروق الإنسان نضح تحت ضغط رقابة وإجهاد القص 2) يدل على أن الكلية التي يسهل اختراقها الخارجية البوليستر شبكة يقلل IH وتوفر معلومات حاسمة لتطبيقه السريرية المحتملة. </p>

<table><tbody><tr><td>RPMI 1640 - Glutamax</td><td>Life Technologies</td><td>61870-010</td><td></td></tr><tr><td>Penicilline/Streptomycine/Fungizone</td><td>Bioconcept</td><td>4-02F00-H</td><td></td></tr><tr><td>Dextran from Leuconostoc spp. 500 g</td><td>Sigma-Aldrich</td><td>31390</td><td></td></tr><tr><td>Tampon PBS CHUV pH 7.1-7.3 1 L</td><td>Laboratorium und Grosse Apotheke Dr. G. Bichsel AG</td><td>100 0 324 00</td><td></td></tr><tr><td>Cryosectionning embedding medium - Tissue-Tek OCT Compound</td><td>Fisher Scientific</td><td>14-373-65</td><td></td></tr><tr><td>Silicon Tubing (Peroxide) L/S 16 (96400-16 ) - 7.5 m</td><td>Idex Health &amp;amp; Science GMBH</td><td>MF0037ST</td><td></td></tr><tr><td>Y-splitter&amp;nbsp;</td><td>Idex Health &amp;amp; Science GMBH</td><td>Y-connector</td><td></td></tr><tr><td>35 mm Culture dish</td><td>Sigma-Aldrich</td><td>CLS430165-100EA</td><td></td></tr><tr><td>15 ml Falcon tube</td><td>BD Bioscence</td><td>352096</td><td></td></tr><tr><td>50 ml Falcon tube</td><td>BD Bioscence</td><td>352098</td><td></td></tr><tr><td>Gearing pump - Reglo-Z</td><td>Idex Health &amp;amp; Science GMBH</td><td>SM 895&amp;nbsp;</td><td>&amp;nbsp;App-Nr 03736-00194</td></tr><tr><td>Pump Head</td><td>Idex Health &amp;amp; Science GMBH</td><td>MI0008&amp;nbsp;</td><td></td></tr><tr><td>Monitoring Kit TRANSPAC IV</td><td>icumedical</td><td>011-0J736-01</td><td></td></tr><tr><td>20 ml Syringes</td><td>B. Braun Medical SA</td><td>4612041-02</td><td></td></tr><tr><td>Etibon 3-0 FS-2</td><td>Ethicon- Johnson&amp;amp;Johnson</td><td>EH7346H</td><td></td></tr><tr><td>Mesh ProVena 6-8mm</td><td>B. Braun Medical SA</td><td>1105012-14</td><td></td></tr><tr><td>NaCl: Sodium chloride solution perfusion 0.9% (100 ml)</td><td>B. Braun Medical SA</td><td>534534</td><td></td></tr><tr><td>Masterflex L/S Standard Drive</td><td>Cole-Parmer Instrument Co</td><td>7521-10</td><td></td></tr><tr><td>Acquisition card</td><td>National Instruments</td><td>PCI-6024 E</td><td></td></tr><tr><td>Flowmeter module</td><td>Transonic Systems Inc.</td><td>TS410 and T402</td><td></td></tr><tr><td>Stopcock with 3-ways</td><td>BD Connexta Luerlock</td><td>394600</td><td></td></tr><tr><td>Millex Filter</td><td>Milian</td><td>SE2M229I04</td><td></td></tr></tbody></table>

procedure for human saphenous veins <em>ex vivo</em> perfusion and external reinforcement

<p class="jove_content" style=";text-align:right;direction:rtl"> عماد العلاجات المعاصرة لمرض الانسداد الشرياني الوريدي واسعة هي الالتفافية الكسب غير المشروع. ومع ذلك، هدد متانته من تضخم باطنة (IH) الذي يؤدي في النهاية إلى انسداد الأوعية وفشل الكسب غير المشروع. القوات الميكانيكية، وإجهاد القص المنخفض وخاصة التوتر العالي الحائط، ويعتقد لبدء ومواصلة هذه التغيرات الخلوية والجزيئية، ولكن يبقى مساهمتها بالضبط إلى أن تفككت. لتقييم انتقائي دور ضغط وإجهاد القص على بيولوجيا IH، تم إنشاء نظام نضح <em>خارج الحي</em> (EVPS) ليروي شرائح الصافن عروق الإنسان في ظل نظام الشرايين (إجهاد القص العالية والضغط العالي). مزيد من الابتكارات التقنية سمحت نضح وقت واحد من جزأين من نفس المنوال، واحدة عززت مع شبكة خارجية. كانت تحصد عروق باستخدام تقنية عدم اللمس ونقل على الفور إلى المختبر لتجميع في EVPS. شريحة واحدة من ISOL طازجةلم perfused لated الوريد (السيطرة، يوم 0). تم perfused لشرائح اثنين آخرين لمدة تصل إلى 7 أيام، واحد يجري محمية تماما مع 4 مم (قطر) شبكة خارجية. الضغط، سرعة التدفق، ومعدل النبض وراقب باستمرار وتعديلها لمحاكاة الظروف السائدة الدورة الدموية في الشريان الفخذي. عند الانتهاء من نضح، تم إلغاء تحميل الأوردة ويستخدم لالنسيجية والتحليل الجزيئي. تحت <em>فيفو السابقين</em> الظروف، نضح الضغط العالي (الشرايين، متوسط ​​= 100 ملم زئبق) كافية لتوليد IH وإعادة تشكيل عروق الإنسان. يتم تخفيض هذه التعديلات في وجود شبكة البوليستر الخارجية. </p>

<p class="jove_content" style=";text-align:right;direction:rtl"> يوفر EVPS أداة قيمة لتقييم مستقل قوات الدورة الدموية في الوريد الصافن البشري الطعوم وإعادة IH. </p><p class="jove_content" style=";text-align:right;direction:rtl"> ويبين <strong>الشكل 1</strong> غرفة نضح والدعم الوريد. في <strong>أرقام 1A</strong> و <strong>B،</strong> ودعم الوريد قبل <strong>(الشكل 1A)</strong> وبعد <strong>(الشكل 1B)</strong> ?...

Watch this Scientific Journal Video about Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement at JoVE.com

Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

<p class="jove_content" style=";text-align:right;direction:rtl"> لا تزال غير مفهومة الآليات التي تؤدي إلى تطوير تضخم باطنة (IH) وفشل الكسب غير المشروع الوريد. توضح هذه الدراسة نظام <em>خارج الحي</em> ليروي عروق الإنسان في ظل التدفق والضغط التي تسيطر عليها. وعلاوة على ذلك تعزيز كفاءة شبكة خارجي للحد تم تقييم تطوير IH. </p>

إجراءات الصافن عروق الإنسان<em&gt; فيفو السابقين</em&gt; الإرواء والتعزيز الخارجي

The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal ...

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Procedure for Human Saphenous Veins <em>Ex Vivo</em> Perfusion and External Reinforcement

11.2K Views.  Brigham and Women's Hospital/Harvard Medical School.  لا تزال غير مفهومة الآليات التي تؤدي إلى تطوير تضخم باطنة (IH) وفشل الكسب غير المشروع الوريد. توضح هذه الدراسة نظام خارج الحي ليروي عروق الإنسان في ظل التدفق والضغط التي تسيطر عليها. وعلاوة على ذلك تعزيز كفاءة شبكة خارجي للحد تم تقييم تط?...

Video: Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

Esterification

<p>Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Esterification<button class="expand">Expand</button>
	<p>In this lab, you will synthesize an ester from a carboxylic acid and an alcohol in the presence of sulfuric acid. This reaction is called Fischer esterification. The sulfuric acid makes the carboxylic acid more reactive towards the alcohol. Without it, esterification would be slow and unfavorable. Esterification is highly reversible, so you&#39;ll use an excess of alcohol to drive the reaction towards the ester.</p>
	<p>You will be assigned one of seven carboxylic acid-alcohol pairs for your reaction. Each of the seven possible product testers has a distinct fruity scent. When you finish the reaction, you will waft your products vapor towards yourself and identify it based on the fruit that it smells like.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-3">
		<div class="lab-step">Before you get started, put on a lab coat, safety glasses, and nitrile gloves. <strong>Note: </strong>Your instructor will demonstrate wafting before handing out the reagents. Always smell compounds by wafting, rather than direct inhalation.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Once you are ready to begin, get your assigned carboxylic acid and alcohol and bring the vials to your fume hood. The vial labeled &#8216;A&#8217;, &#8216;B&#8217;, or &#8216;C&#8217; is your carboxylic acid. The other vial is the alcohol. Record the letters of your carboxylic acid and alcohol in your lab notebook.
		<h4><strong>Table 1: Scent of Carboxylic Acid, Alcohol, and Ester</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td></td>
					<td><strong>Letter </strong></td>
					<td><strong>Scent </strong></td>
				</tr>
				<tr>
					<td>Assigned carboxylic acid</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Assigned alcohol</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Synthesized ester</td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/68/Table_1._Scent_of_carboxylic_acid,_alcohol,_and_ester.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Now, get a piece of filter paper and a Pasteur pipette. In the fume hood, use the Pasteur pipette to apply a drop of your alcohol to the filter paper.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Bring the filter paper to the front of the hood and waft the scent of the alcohol towards yourself. Be careful because it might smell unpleasant.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Then, put the filter paper back in the hood and write a brief description of the scent of the alcohol in your lab notebook. Do the same for your carboxylic acid if it&#39;s a liquid using a new pipette and piece of filter paper. <strong>Note:</strong> If you were assigned a solid carboxylic acid, write &#39;solid&#39; in your lab notebook and skip this step.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Now, attach an open 3-prong clamp to a lab stand in your fume hood. Place a lab jack at the base of the stand and set a stir plate and a heating mantle on top of it. Move the temperature controller next to the setup.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Then, place a small stir bar in a 50-mL round-bottom flask and securely clamp the flask over the heating mantle.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Add the carboxylic acid to the flask using a funnel. Rinse the carboxylic acid vial into the flask with 1 or 2 mL of your alcohol, and then add the rest of the alcohol to the flask.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Next, bring a 10-mL graduated cylinder to the fume hood reserved for acids, and carefully measure 4 mL of 3 M sulfuric acid. <strong>Note:</strong> It&#39;s highly toxic and corrosive, so be careful with it.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Cover your graduated cylinder with plastic paraffin film. Then, bring the acid back to your hood and add it to the flask. It&#39;s OK if the liquids form two layers.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Now, use one piece of tubing to connect the lower arm of the standard condenser to the water tap in your fume hood. Attach the other piece of tubing to the upper arm and direct it to your drain. Make sure that the connections are secure.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Apply vacuum grease to the lower ground glass joint of the condenser. Fit the condenser into the round-bottom flask and ensure that the grease forms a good seal.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Secure the condenser in place with a second 3-prong clamp and make sure that the tubing is out of the way. Use a laboratory wipe to remove excess grease, and then secure the connection with a joint clip.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Now, slowly open the water tap until water is flowing smoothly through the condenser. Make sure that the water is flowing into the drain and that there are no leaks.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Then, raise the lab jack until the round-bottom flask is sitting in the heating mantle. You are now ready to start heating your reaction mixture to reflux.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Set the stir motor to medium speed and start heating the mixture on medium heat or with a set point of about 110 &#176;C.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">The first boiling point of your mixture will be between 65 and 100 &#176;C. So, keep an eye on it as it heats and adjust the temperature setting as needed.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Once the mixture reaches an even boil, let it reflux for 50 min.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Then, turn off the heat, lower the lab jack, and replace the heating mantle with a round bottom flask holder.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">Let the mixture cool to room temperature with the condenser still in place, which usually takes about 10 min. During that time, prepare an ice bath in a 600-mL beaker and bring it to your fume hood.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Once the mixture has cooled completely, turn off the flow of water to the condenser. Carefully separate the condenser from the flask and move it out of the way. Then, raise the ice bath up to the flask and let it cool for 10 min.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">After that, bring a clean 10-mL graduated cylinder to the base hood and obtain 5 mL of saturated sodium bicarbonate.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Back at your hood, use a lab wipe to remove vacuum grease from the inside of the neck of the round bottom flask.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Then, obtain several clean Pasteur pipettes and some pH paper. Use a pipette to slowly add 1 mL of saturated sodium bicarbonate to the flask and stir the mixture with a stir bar or a glass rod.</div>
		</li>
		<li data-sub-note-item="1-27">
		<div class="lab-step">Add the rest of the sodium bicarbonate solution a milliliter at a time, stirring after each addition.</div>
		</li>
		<li data-sub-note-item="1-28">
		<div class="lab-step">Then, use a new pipette to check the pH of the solution. If the pH is &#60; 7, get a few more milliliters of sodium bicarbonate and add it 1 mL at a time, stirring and checking the pH after each addition.</div>
		</li>
		<li data-sub-note-item="1-29">
		<div class="lab-step">Once the solution is at a neutral pH, remove the ice bath and dry the outside of the flask with a paper towel.</div>
		</li>
		<li data-sub-note-item="1-30">
		<div class="lab-step">Let the mixture sit for a few minutes to see whether it settles into two layers.</div>
		</li>
		<li data-sub-note-item="1-31">
		<div class="lab-step">Then, obtain a clean Pasteur pipette and a new piece of filter paper. Carefully draw up a small amount of the product solution and apply one or two drops to the filter paper. If your product mixture separated, test the top layer first.</div>
		</li>
		<li data-sub-note-item="1-32">
		<div class="lab-step">Bring the filter paper to the edge of the fume hood and waft the set towards yourself. The seven possible scents are apple, banana, grape, orange, pear, pineapple, and strawberry.</div>
		</li>
		<li data-sub-note-item="1-33">
		<div class="lab-step">Record the fruit that you think your ester smells like in your lab notebook. If you aren&#39;t sure which fruit it is, ask your instructor for the reference scents to help you decide.</div>
		</li>
		<li data-sub-note-item="1-34">
		<div class="lab-step">Once you&#39;ve identified the smell of your ester, retrieve the stir bar, and dispose of your reaction mixture in the non-halogenated organic waste container. Clean your glassware and stir bar using your usual methods.</div>
		</li>
		<li data-sub-note-item="1-35">
		<div class="lab-step">Next, unclamp the condenser and carefully tilt it to let the water drain through the outlet tubing. Disconnect the inlet tubing from the water tap, keeping the end raised to avoid spills, and let the remaining water flow through the condenser to the drain.</div>
		</li>
		<li data-sub-note-item="1-36">
		<div class="lab-step">Then, disconnect the condenser from the tubing and remove the vacuum grease on the bottom joint with lab wipes. Clean the inner walls of the condenser using your usual methods.</div>
		</li>
		<li data-sub-note-item="1-37">
		<div class="lab-step">Leave the filter papers in the hood until they stop smelling strongly of fruit. Dispose of used Pasteur pipettes in the glass waste and throw out any other trash in the lab trash container.</div>
		</li>
		<li data-sub-note-item="1-38">
		<div class="lab-step">Lastly, put away your equipment and clean your hood before you leave.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Results<button class="expand">Expand</button>
	<p>Here are the seven possible esters that you could have made and their scents: propyl acetate smells like pear, isoamyl acetate smells like banana, octyl acetate smells like orange, butyl butyrate smells like pineapple, ethyl butyrate smells like strawberry, methyl butyrate smells like apple, and methyl anthranilate smells like grape.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-2">
		<div class="lab-step">Compare the scent of your ester to find the corresponding structure. For example, a strong scent of pears means that you made propyl acetate.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Determine your starting carboxylic acid and alcohol. <strong>Note: </strong>Remember that alcohol attacks the carboxylic acid in this reaction. The resulting intermediate rearranges and eliminates a water molecule to form an ester.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Studies have shown that the alkoxy oxygen comes from the alcohol, not the carboxylic acid. So, we&#39;ll split the ester diagram at the carbon-oxygen single bond and fill in the missing OH and H to get the starting materials. For example, if we split propyl acetate at that bond, add an OH to the carbonyl carbon and add a hydrogen to the alkoxy oxygen, we get acetic acid and 1-propanol as the starting materials.</div>
		</li>
	</ul>
	</li>
</ol>

Esterification: Synthesis of Ester by Fischer Esterification - Procedure

الأسترة

Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA

	EsterificationExpand
	In this lab, you will synthesize an ester from a ...

Education

JoVE Lab Manual

Chemistry

Lab Manual Sub Articles

Buffers

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse=""><strong>Preparing 50 mM NaH<sub>2</sub>PO<sub>4</sub> Buffer, pH 7</strong><button class="expand">Expand</button>
	<p>In the first part of this experiment, you will prepare a sodium phosphate solution buffered at pH 7.0. Monosodium phosphate is a weak acid with the conjugate base, disodium phosphate. Unadjusted monosodium phosphate solutions usually have a pH of about 4 - 6.</p>
	<p>Buffers are most effective close to their pKa, which is 6.8 to 7.2 for monosodium phosphate. So, you will use NaOH to push the equilibrium towards the conjugate base without altering the overall composition of the buffer equilibrium.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-3">
		<div class="lab-step">Before starting the experiment, calculate the mass of monosodium phosphate that you will need to make 200 mL of a 50 mM solution.
		<h4><strong>Table 1: Preparation of 50 mM NaH<sub>2</sub>PO<sub>4</sub> Buffer, pH 7.0</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always" height="247" width="358">
			<tbody>
				<tr>
					<td colspan="2"><strong>Molar mass of NaH<sub>2</sub>PO<sub>4</sub> = 119.98 g/mol</strong></td>
				</tr>
				<tr>
					<td>Solution volume (mL)</td>
					<td style="text-align: center;">200</td>
				</tr>
				<tr>
					<td>Molarity (mM)</td>
					<td style="text-align: center;">50</td>
				</tr>
				<tr>
					<td>Moles of NaH<sub>2</sub>PO<sub>4</sub> (mol)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Mass needed (mg)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Initial volume of 1 M NaOH (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Final volume of 1 M NaOH (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Volume of NaOH used (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Volume of DI water needed (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/45/Table_1._Preparation_of_50_mM_NaH2PO4_Buffer,_pH_7.0.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">To begin, put on the necessary personal protective equipment, including a lab coat, splash-resistant safety glasses, and gloves. <strong>Note: </strong>This section of the lab uses NaOH, which is corrosive and toxic. Use caution when pouring and transporting NaOH.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Fill a 250-mL plastic wash bottle with deionized water.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Label two 100-mL beakers, one for neutral aqueous waste and one for basic aqueous waste.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Calibrate your pH meter using the provided buffers. Store the probe in its storage solution when you are done.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Tare weighing paper, and use a clean spatula to measure out the required amount of monosodium phosphate according to your calculations. Record the exact amount of monosodium phosphate in your lab notebook. <strong>Note: </strong>Monosodium phosphate absorbs moisture from the air, so work quickly to obtain an accurate measurement and close the container tightly when you are done with it.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Place the monosodium phosphate in a 400-mL beaker and clean the spatula with a laboratory wipe. Throw out the weighing paper and the laboratory wipe before returning to your fume hood.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Use a graduated cylinder to measure out 175 mL of deionized water. Pour the water into the beaker of monosodium phosphate and add a magnetic stir bar.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Stir the solution until the salt has dissolved completely and the solution appears homogeneous. This usually takes 2 - 3 min.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Measure 15 mL of deionized water and pour it into the beaker. Continue stirring the solution until it appears homogeneous again (about 1 &#8211; 2 min). Turn off the stir motor.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Rinse the pH probe with deionized water, and then clamp it in the solution with the sensor above the stir bar.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Bring a 10-mL graduated cylinder and watch glass to the dispensing hood and measure out 10 mL of 1 M NaOH. Note the exact volume in the graduated cylinder.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Cover your NaOH with the watch glass, and carefully bring it to your fume hood.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Resume stirring the monosodium phosphate solution. While monitoring the pH reading, use a disposable pipette to slowly add NaOH to the stirring solution in a drop-wise manner. Once the buffer pH reaches 7.0, return any NaOH still in the pipette to the graduated cylinder.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Calculate the volume of NaOH that you added to the buffer. Subtract that volume from 10 mL to determine how much deionized water you must add to your buffer to reach a total solution volume of 200 mL.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Measure the deionized water with another 10-mL graduated cylinder and add it to the stirring solution to finish making the buffer.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Rinse the pH sensor with deionized water, cover it with the storage solution filled cap, and unplug or turn off the probe.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Label a 250-mL polyethylene bottle as &#39;50 mM monosodium phosphate buffer, pH 7.0&#39;. Retrieve the magnetic stir bar from the solution.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Use a funnel to pour the buffer solution into the labeled bottle and cap it tightly.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse=""><strong>Absorption Spectroscopy of Free and Bound Neutral Red</strong><button class="expand">Expand</button>
	<p>Buffers can be used to evaluate compounds at specific pH values. In this section, you will record the absorbance spectrum of the indicator neutral red in various buffers. The protonated form of neutral red is red, and the deprotonated form is yellow-orange, meaning that they absorb green and blue-violet light, respectively. Thus, the acidic and basic forms have distinct absorption wavelengths. Protein binding alters the properties of neutral red, changing both its absorbance and its pKa.</p>
	<p>After measuring the absorbance spectrum of free neutral red at several pH values, you will add riboflavin-binding protein, or RP, to the solutions and measure the absorbances again. Absorbance intensity is related to concentration, so you will use the spectra to determine the pKa of free and bound neutral red after the lab.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-3">
		<div class="lab-step">Draw the following table in your lab notebook. Number the cuvettes 1 through 10 and list the nine buffer pH values that you will use. The 10th cuvette will be a deionized water blank. <strong> Note: </strong>Always hold cuvettes by the textured sides and wipe the transparent sides just before putting the cuvette in the spectrophotometer. Remember to align the transparent sides with the beam of light in the spectrophotometer.
		<h4><strong>Table 2: Absorbance of Free and Bound Neutral Red</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td style="text-align: center;"><strong>Cuvette #</strong></td>
					<td style="text-align: center;"><strong>Buffer pH </strong></td>
					<td style="text-align: center;"><strong>Abs. at &#955;<sub>max </sub>(Free NRH<sup>+</sup>)</strong></td>
					<td style="text-align: center;"><strong>Abs. at &#955;<sub>max</sub> (Bound NRH)</strong></td>
				</tr>
				<tr>
					<td style="text-align: center;">1</td>
					<td style="text-align: center;">5.0</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">2</td>
					<td style="text-align: center;">5.5</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">3</td>
					<td style="text-align: center;">6.0</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">4</td>
					<td style="text-align: center;">6.5</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">5</td>
					<td style="text-align: center;">7.0</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">6</td>
					<td style="text-align: center;">7.5</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">7</td>
					<td style="text-align: center;">8.0</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">8</td>
					<td style="text-align: center;">8.5</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">9</td>
					<td style="text-align: center;">11</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">10</td>
					<td style="text-align: center;">blank</td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/45/Table_2._Absorbance_of_Free_and_Bound_Neutral_Red.xlsx" target="_blank">Click Here to download Table 2</a></div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Obtain ten 1.5-mL cuvettes and caps and label the caps 1 through 10 to match the table in your lab notebook.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Label a 25-mL beaker as &#8216;DIH2O&#8217; and fill it with deionized water.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Flush your neutral aqueous waste down the drain and relabel the beaker as &#39;aqueous buffer waste&#39;.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Label a 400-mL beaker for used micropipette tips.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Attach a tip to a 1-mL micropipette and use it to dispense 1000 &#181;L of deionized water into cuvette 10. This is your solvent blank.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Place 925 &#181;L of your pH 7.0 monosodium phosphate buffer in cuvette 5.</div>
		</li>
		<li data-sub-note-item="2-10">
		<div class="lab-step">Bring the remaining empty cuvettes to the buffer table. Guided by the table in your lab notebook, dispense 925 &#181;L of each buffer into the appropriate cuvette using the labeled micropipettes. Be careful not to use the same pipette tip for different buffers.</div>
		</li>
		<li data-sub-note-item="2-11">
		<div class="lab-step">Once you have finished, bring the buffers back to your workbench. There, set a 200-&#181;L micropipette to dispense 75 &#181;L, and attach a tip to the micropipette.</div>
		</li>
		<li data-sub-note-item="2-12">
		<div class="lab-step">Dispense 75 &#181;L of neutral red into each of the nine buffer cuvettes. Invert each cuvette several times to thoroughly mix the solutions. <strong>Note: </strong>Replace the pipette tip if it touches a buffer.</div>
		</li>
		<li data-sub-note-item="2-13">
		<div class="lab-step">Once you have mixed neutral red with every buffer, take a picture, or write down the colors of the solutions.</div>
		</li>
		<li data-sub-note-item="2-14">
		<div class="lab-step">Turn on a hand-held spectrophotometer and allow the light source to warm up. Once it is ready, create a new experiment to measure absorbance versus wavelength for the free neutral red.</div>
		</li>
		<li data-sub-note-item="2-15">
		<div class="lab-step">Insert the cuvette of deionized water and acquire a spectrum of the deionized water. Set it as a solvent background or blank.</div>
		</li>
		<li data-sub-note-item="2-16">
		<div class="lab-step">Then, remove the blank and insert the cuvette of neutral red in the lowest pH buffer, which will have the highest concentration of protonated neutral red.</div>
		</li>
		<li data-sub-note-item="2-17">
		<div class="lab-step">Acquire a spectrum, which should show one strong peak. Identify the wavelength corresponding to the highest point of this peak, or the maximum. Record this wavelength in your lab notebook as lambda max for protonated free neutral red.</div>
		</li>
		<li data-sub-note-item="2-18">
		<div class="lab-step">Save the data and remove the cuvette. Record the absorbance in your notebook, then collect spectra for cuvettes 2 - 9 using the same procedure.</div>
		</li>
		<li data-sub-note-item="2-19">
		<div class="lab-step">Record the wavelength of the isosbestic point in your lab notebook. That is where all the spectra cross at a single wavelength. If a spectrum does not cross at that point, empty and clean the cuvette, prepare a fresh sample, and try again.</div>
		</li>
		<li data-sub-note-item="2-20">
		<div class="lab-step">Once you finish collecting spectra for all nine cuvettes, save and export the data.</div>
		</li>
		<li data-sub-note-item="2-21">
		<div class="lab-step">Create a new experiment to measure absorbance versus wavelength for the bound neutral red.</div>
		</li>
		<li data-sub-note-item="2-22">
		<div class="lab-step">Fit a new tip to the 200-&#181;L micropipette and add 75 &#181;L of riboflavin-binding protein solution to each cuvette, including the blank. Eject the tip, secure the cuvette caps, and invert the cuvette several times to mix the solutions.</div>
		</li>
		<li data-sub-note-item="2-23">
		<div class="lab-step">Insert cuvette 10 into the spectrophotometer and set it as the solvent blank.</div>
		</li>
		<li data-sub-note-item="2-24">
		<div class="lab-step">Acquire a spectrum of the lowest pH sample, and identify the wavelength corresponding to the maximum of the most intense peak. Record it in your lab notebook as the lambda max of protonated-bound neutral red.</div>
		</li>
		<li data-sub-note-item="2-25">
		<div class="lab-step">Acquire spectra for cuvettes 2 - 9 in the same way as you did for the free neutral red samples. Record the intensities at lambda max for protonated-bound neutral red in your table, along with the wavelength at the isosbestic point.</div>
		</li>
		<li data-sub-note-item="2-26">
		<div class="lab-step">When you are done, save your data, export it for later analysis, and shut down the spectrophotometer.</div>
		</li>
		<li data-sub-note-item="2-27">
		<div class="lab-step">Put away all equipment and dispose of your used pipette tips in an approved waste container or trash bin.</div>
		</li>
		<li data-sub-note-item="2-28">
		<div class="lab-step">Empty the cuvettes into the aqueous buffer waste beaker and rinse the cuvettes into the beaker with deionized water.</div>
		</li>
		<li data-sub-note-item="2-29">
		<div class="lab-step">Empty the excess NaOH into the basic waste and rinse the graduated cylinder with water.</div>
		</li>
		<li data-sub-note-item="2-30">
		<div class="lab-step">Flush the basic aqueous waste down the drain with copious tap water, along with the other aqueous waste.</div>
		</li>
		<li data-sub-note-item="2-31">
		<div class="lab-step">Wash your glassware, cuvette caps, and stir bar per your lab standard procedures. Clean your work surfaces with a damp paper towel and throw out used paper towels and lab wipes in the lab trash.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="3" data-parent-collapse=""><strong>Results</strong><button class="expand">Expand</button>
	<p>Now, let&#39;s analyze our absorbance data to determine the pKa&#39;s of neutral red.</p>
	<h4><strong>Table 3: Determination of Neutral Red pKa&#39;s</strong></h4>
	<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
		<tbody>
			<tr>
				<td></td>
				<td>Free NRH<sup>+</sup></td>
				<td>Bound NRH<sup>+</sup></td>
			</tr>
			<tr>
				<td>&#160;&#955;<sub>max</sub> (nm)</td>
				<td></td>
				<td></td>
			</tr>
			<tr>
				<td>&#160;&#916;A (nm)</td>
				<td></td>
				<td></td>
			</tr>
			<tr>
				<td>&#160;Midpoint (nm)</td>
				<td></td>
				<td></td>
			</tr>
			<tr>
				<td>&#160;pKa</td>
				<td></td>
				<td></td>
			</tr>
		</tbody>
	</table>
	<p><a href="https://www.jove.com/CDNSource/lm/labs/45/Table_3._Determination_of_Neutral_Red_pKa.xlsx" target="_blank">Click Here to download Table 3</a></p>
	<ul class="lab-items">
		<li data-sub-note-item="3-2">
		<div class="lab-step">Plot both sets of intensity data with absorbance intensity at lambda max on the y-axis and pH on the x-axis, with the points joined by smooth lines.</div>
		</li>
		<li data-sub-note-item="3-3">
		<div class="lab-step">Calculate the difference between the starting and ending absorbance intensities for each data series.</div>
		</li>
		<li data-sub-note-item="3-4">
		<div class="lab-step">Determine the absorbance midway between the starting and ending absorbances for each series, or the absorbance midpoints.</div>
		</li>
		<li data-sub-note-item="3-5">
		<div class="lab-step">Find where the midpoint occurs on each line and identify the pH value at that point. These pH values are the pKa&#39;s of free and bound neutral red.</div>
		</li>
		<li data-sub-note-item="3-6">
		<div class="lab-step">Here, we see an increase in pKa of about one between free and bound neutral red, indicating that bound-protonated neutral red is a weaker acid than free protonated neutral red by an order of magnitude.</div>
		</li>
	</ul>
	</li>
</ol>

Buffers: Common Ion Effect, Henderson-Hasselbalch Equation, and Buffer Capacity - Procedure

المخازن المؤقته

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Preparing 50 mM NaH2PO4 Buffer, pH 7Expand
	In the first part of this experiment, you will ...

Galvanic Cells

Galvanic Cells: Construction and Reduction Potential Measurement - Procedure

الخلايا الجلفانية

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Constructing a Lead-Copper Galvanic CellExpand
	In this experiment, you will construct a ...

Extraction

Extraction: Liquid-Liquid and Acid-Base Extraction - Procedure

إستخلاص

Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA

	Cellulose RecoveryExpand
	Extraction and filtration can ...

Steam Distillation

<p>Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Steam Distillation<button class="expand">Expand</button>
	<p>In this experiment, you will perform a steam distillation to extract an essential oil from an orange peel.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-2">
		<div class="lab-step">Before you start the lab, put on the appropriate personal protective equipment, including a lab coat, safety goggles, and gloves. This experiment must be performed in a hood.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">First, you will need to assemble the steam distillation apparatus. Check the apparatus set up by your instructor.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Set the two stands next to each other in the hood. Place the stir plate on the base of one of the stands and set the heating mantle on top of it. Plug the heating mantle into the temperature controller, but do not turn it on yet.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Now, obtain a watch glass with 3 dried orange peels from your instructor. Weigh the orange peels on the balance and record the mass of the orange peels in your notebook.
		<h4><strong>Table 1: Mass of essential oil recovered</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always" height="166" width="476">
			<tbody>
				<tr>
					<td>Temperature of steam distillation (&#176;C)</td>
					<td></td>
				</tr>
				<tr>
					<td>Mass of the orange peels (g)</td>
					<td>&#160; &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
				</tr>
				<tr>
					<td>Mass of empty flask (g)</td>
					<td></td>
				</tr>
				<tr>
					<td>Mass of flask + essential oils (g)</td>
					<td></td>
				</tr>
				<tr>
					<td>Mass of essential oils (g)</td>
					<td></td>
				</tr>
				<tr>
					<td>Percent mass of essential oil recovered</td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/61/Table_1._Mass_of_essential_oil_recovered.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Bring your dried peels, funnel, spatula, and the 500-mL round-bottom flask to the instructor&#39;s bench and place the peels in the blender. Add about 4 mL of deionized water to the peels. Then, blend them until they are well mixed and smooth.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Using the funnel, transfer the blended peels to the round-bottom flask. Clamp the flask to the stand above the heating mantle.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Measure 200 mL of deionized water using your graduated cylinder and transfer it to the round-bottom flask using a funnel. Remove the funnel and add a stir bar to the flask.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Locate the Claisen adapter and apply a thin layer of grease to the joint. Then, insert the Claisen adapter into the flask.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Grease the thermometer adapter and insert it into the distilling head.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Gently insert the thermometer into the distilling head by pushing and twisting through the adapter until the thermometer bulb is below the bend of the distilling head.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Lightly grease the lower joint of the distilling head, and then insert it into the outer arm of the Claisen adapter.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Now, obtain the condenser and carefully clamp it to the second stand. It should be oriented nearly horizontally, with the end closest to the distilling head slightly higher.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Lightly grease the condenser and the side joint of the distilling head before connecting them.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Next, attach one piece of rubber tubing to the inlet of the condenser, which is the port furthest away from the distilling head. Attach the other end to the tap water faucet in the hood.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Connect the second piece of rubber tubing to the other port, which is the outlet, and place the end of the tubing in the drain.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Locate the separatory funnel and make sure that the stopcock is closed by turning it until it is fully horizontal.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Insert the separatory funnel into the Claisen adapter, and add approximately 100 mL of deionized water to the funnel.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Pick up the connecting joint and attach it to the end of the condenser.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Then, attach a 250-mL round-bottom flask to the connecting joint using a plastic clip.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Finally, check all of the joints to make sure they are tightly connected and then secure each one with a plastic clip.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">Now that the steam distillation apparatus is fully assembled, start the procedure. First, slowly turn the tap water on to fill the condenser with water. <strong>Note</strong>: Be sure to turn the water on slowly, or the tubing may pop off and cause a flood.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Next, turn on the magnetic stirrer at the lowest setting and set the temperature controller to the appropriate setting to reach about 90 &#176;C.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Once bubbles start forming in the mixture and liquid is dripping into the collection flask, adjust the heat to increase or decrease the rate of distillation to about 20 drops/min.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Record the temperature on the thermometer in your notebook. Now, carefully open the stopcock on the separatory funnel to slowly add water to the flask. Your goal is to add water at the same rate as distillation, about 20 drops/min.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Allow the distillation to proceed and collect about 50 mL of distillate.<strong> Note:</strong> Be patient, since this should take about 2 hours. The liquid in the flask will become less cloudy as more oil is collected.</div>
		</li>
		<li data-sub-note-item="1-27">
		<div class="lab-step">Once you have collected enough distillate, turn off the heat. Then, shut off the water to the condenser and carefully raise the entire setup.</div>
		</li>
		<li data-sub-note-item="1-28">
		<div class="lab-step">Allow it to cool completely before removing the heating mantle and disassembling the glassware.</div>
		</li>
		<li data-sub-note-item="1-29">
		<div class="lab-step">Empty the separatory funnel of any remaining water and pour the orange pulp down the drain.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Extraction of Essential Oil<button class="expand">Expand</button>
	<p>Liquid-liquid extraction is performed in a separatory funnel and is used to move a solute to another liquid in which it is more soluble. The two liquids must be immiscible and are usually an aqueous solution and a non-water-soluble organic liquid. Upon mixing, the solute is extracted into the other phase. Once the liquids settle into layers, they can be drained from the funnel one at a time.</p>
	<p>In the next part of the experiment, liquid-liquid extraction will be used to extract the essential oil from the water into an organic solvent. You&#39;ll then evaporate the organic solvent to recover the essential oil.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-3">
		<div class="lab-step">Before starting the experiment, first, make sure that the separatory funnel is rinsed and clean.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Label the two 250-mL beakers as &#8216;organic layer&#8217; and &#8216;aqueous layer&#8217;. Then, attach a ring support to one of the stands.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Place the separatory funnel in the support. Make sure that the stopcock is closed and the separatory funnel is secure. Then, transfer the distillate into the separatory funnel.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Measure 20 mL of diethyl ether at the instructor&#39;s hood and bring it back to your workstation. Pour the diethyl ether into the separatory funnel with the distillate. <strong>Note:</strong> You should see the immiscible liquids form two layers in the funnel. The top layer is the diethyl ether.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Apply a thin layer of vacuum grease to the separatory funnel stopper and insert it into the top of the funnel.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Hold the stopper in place and shake the separatory funnel vigorously for about 1 min.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Occasionally, vent the funnel by turning it upside down and opening, then closing the stopcock. Be sure to do this inside of the hood and away from your face.</div>
		</li>
		<li data-sub-note-item="2-10">
		<div class="lab-step">Once you have finished mixing the contents, vent the funnel again, close the stopcock, and then place the funnel in the ring attached to the stand.</div>
		</li>
		<li data-sub-note-item="2-11">
		<div class="lab-step">Allow the aqueous and organic layers to fully separate. Then, place the aqueous layer beaker under the separatory funnel.</div>
		</li>
		<li data-sub-note-item="2-12">
		<div class="lab-step">Remove the stopper and slowly open the stopcock to drain the aqueous layer into the beaker. Carefully watch the solution drain and be sure to close the stopcock before the next layer is drained.</div>
		</li>
		<li data-sub-note-item="2-13">
		<div class="lab-step">Replace the aqueous layer beaker with the organic layer beaker. Open the stopcock and drain the organic layer into its beaker.</div>
		</li>
		<li data-sub-note-item="2-14">
		<div class="lab-step">Now, close the stopcock and return the contents of the aqueous layer beaker to the separatory funnel, add 20 mL of diethyl ether, and repeat the extraction.</div>
		</li>
		<li data-sub-note-item="2-15">
		<div class="lab-step">Open the stopcock and drain the aqueous layer into the appropriate beaker, and then drain the organic layer into the organic layer beaker, adding it to the organic layer from the first extraction.</div>
		</li>
		<li data-sub-note-item="2-16">
		<div class="lab-step">Now, obtain magnesium sulfate in a weighing boat and scoop a small spatula of it into the organic layer beaker. Swirl the beaker, and then let it sit for about 20 min.</div>
		</li>
		<li data-sub-note-item="2-17">
		<div class="lab-step">After 20 min, remove the separatory funnel and ring and mount a regular clamp to the lab stand.</div>
		</li>
		<li data-sub-note-item="2-18">
		<div class="lab-step">Weigh an empty 125-mL Erlenmeyer flask and record the mass in your notebook. Then, clamp the flask to the stand and place a conical glass funnel in its neck.</div>
		</li>
		<li data-sub-note-item="2-19">
		<div class="lab-step">Fold your filter paper in half and in half again. Then, open the filter paper on one side to create a cone. Place the cone inside the conical funnel.</div>
		</li>
		<li data-sub-note-item="2-20">
		<div class="lab-step">Now, filter the magnesium sulfate from the organic layer.</div>
		</li>
		<li data-sub-note-item="2-21">
		<div class="lab-step">Next, set your hot plate to 40 &#176;C and place a large beaker containing 400 mL of water on it. Place the Erlenmeyer flask in the warm water bath and allow the organic solvent to evaporate in the hood.</div>
		</li>
		<li data-sub-note-item="2-22">
		<div class="lab-step">Once the organic solvent has fully evaporated, remove the Erlenmeyer flask from the water bath and dry the outside with paper towels.</div>
		</li>
		<li data-sub-note-item="2-23">
		<div class="lab-step">Weigh the cooled flask and record the mass in your notebook.</div>
		</li>
		<li data-sub-note-item="2-24">
		<div class="lab-step">Now that the experiment is complete, be sure to properly clean up your workspace by disposing of all solutions in the non-halogenated waste.</div>
		</li>
		<li data-sub-note-item="2-25">
		<div class="lab-step">Wash all of the glassware using detergent and then rinse them with acetone and deionized water.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="3" data-parent-collapse="">Results<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="3-1">
		<div class="lab-step">Determine the mass of the oil extracted from the orange peel by subtracting the mass of the empty flask from the mass of the flask with oil.</div>
		</li>
		<li data-sub-note-item="3-2">
		<div class="lab-step">Calculate the percentage of oil in the orange peel using the original mass of the dried peel. Typically, the steam distillation method recovers about 0.9 &#8211; 4 wt% of an orange peel&#8217;s mass as essential oil.</div>
		</li>
	</ul>
	<p>You distilled the essential oil in this lab at close to 100 &#176;C. The orange oil consists mainly of (+)limonene, which has a boiling point of 176 &#176;C. Thus, the steam distillation technique lets us extract it from the orange peel at a temperature that will not compromise its structure.</p>
	</li>
</ol>

Steam Distillation: Extraction of Essential Oil from Orange Peel - Procedure

التقطير بالبخار

Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA

	Steam DistillationExpand
	In this experiment, you will ...

Thin-Layer Chromatography

<p>Source: Lara Al Hariri and&#160;Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Effects of Mobile Phase Composition on Compound Separation<button class="expand">Expand</button>
	<p>In this section of the lab, you will use TLC to compare how well pure hexane and a mixture of 60% hexane and 40% ethyl acetate can separate phenol, benzoic acid, and butyl phenyl ether by measuring the distance the compound traveled in each solvent.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-2">
		<div class="lab-step">Before starting the lab, put on a lab coat, safety glasses, and nitrile gloves. Note: Hexane and ethyl acetate are both volatile, toxic, and flammable, so always work with them in a fume hood. Change your gloves if you get solvent on them, as hexane and ethyl acetate will permeate nitrile gloves within minutes.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Now, obtain a paper towel and lay it on the benchtop. Carefully pick up a TLC plate using tweezers at the very end of the plate.<strong> Note: </strong>Always hold TLC plates by the edges or at the very top with tweezers to avoid damaging or contaminating the silica gel.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Look for chips or scratches in the silica gel and get a new plate if necessary. It&#39;s fine if there is a little chipping at only one end, since that can be the top.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Place the plate on the paper towel in your fume hood, and lay a metric ruler next to it. Use a graphite pencil to gently make a small mark on the silica gel ~1 cm from the top of the plate. Write &#8216;100&#8217; on the plate above the mark.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Next, gently mark the plate 1 cm above the bottom on both sides. Carefully trace a straight line between the bottom marks to make the starting line.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Then, add 3 evenly spaced small marks to the starting line with the outer marks at least 0.5 cm from the sides of the plate. <strong>Note:</strong> It&#39;s important for the silica gel to be undamaged here, so if you scratch it with the pencil, prepare a new plate.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Now, trace the outline of the TLC plate in your lab notebook and precisely copy the marks on the plate. Label the three marks as &#8216;phenol&#8217;, &#8216;benzoic acid&#8217;, and &#8216;butyl phenyl ether&#8217;. You may also want to label the marks on the plate itself.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Prepare a second TLC plate labeled &#8216;60/40&#8217; in the same way. Now, bring the labeled plates to the common bench and locate the 1 mg/mL solutions of phenol, benzoic acid, and butyl phenyl ether in ethanol.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Dip a clean capillary into one of the three solutions. Briefly and lightly dab the capillary squarely against the intersection between the starting line and the mark for that compound. You should spot twice for each compound.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Use the same capillary to spot the same solution on your second TLC plate. The spots should be no more than 2 mm in diameter. Then, discard the capillary and close the vial.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Spot the other two solutions on the plates, in the same way, using clean capillaries. Be careful not to cross-contaminate the solutions. <strong>Note</strong>: If a spot is very light or very small, wait for it to dry, and then spot the same solution on top of the dry spot. If the spot is still wet, capillary action could make it too wide and dilute.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Once you have made three spots on each plate, discard the capillaries and bring the plates back to your hood. Keep the plates lying flat while they dry.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Now, label a 50-mL jar &#8216;100% hexane&#8217; and bring the jar, its cap, and a 10-mL graduated cylinder to the solvent hood.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Measure 2 &#8211; 3 mL of pure hexane with your graduated cylinder and pour it into the jar to fill it to a depth of 0.62 &#8211; 0.7 cm. Cap the bottle and jar and return to your fume hood.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Label a second 50-mL jar &#8216;60% hexane, 40% ethyl acetate&#8217; and bring it and a clean graduated cylinder to the solvent hood. Measure 2 &#8211; 3 mL of the 60/40 mixture into the jar and return to your fume hood.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Stand the plates next to the jars to compare the relative position of the solvent and the spots. The solvent level should be below the spots for each plate.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Then, obtain three pieces of filter paper, put a filter paper upright against the wall in each jar, and then cap the jars tightly.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Initial each plate above the mark so you can identify them later. Confirm that the filter papers in the jars have become saturated with solvent and that the spots on the plates are completely dry.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Now, open the 100% hexane jar and use tweezers to gently place the 100 plate in the jar, keeping the plate level with the solvent surface as it enters the solvent. Close the jar tightly, being careful not to jostle the plate.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Leave the jar still as the solvent travels up the plate. Development in pure hexane usually takes about 7 &#8211; 10 min. Keep an eye on the plate to make sure that the solvent doesn&#39;t reach the top.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">When the pure hexane solvent front is about 1 cm from the top of the plate, retrieve it using tweezers. Lay it on the paper towel with the silica gel facing up and quickly mark the solvent front with a line and pencil across the plate. Leave the plate lying flat as the solvent evaporates.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Place the other plate in the 60/40 eluent in the same way. Wait until the solvent front of the 60/40 plate is about 1 cm from the top, and then retrieve it and quickly mark the solvent front in the same way.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Once the 100% hexane plate is completely dry, pick it up with tweezers and bring it and a pencil to the UV lamp on the common bench.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Place the plate under the lamp and illuminate it with UV light. The plate will glow green because of a fluorescent marker in the silica gel layer. The dark spots are the compounds.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Carefully outline every spot in pencil, even if they haven&#39;t moved very far.</div>
		</li>
		<li data-sub-note-item="1-27">
		<div class="lab-step">Then, turn off the lamp and bring your plate to the iodine development hood. Open the iodine chamber. Use tweezers to gently place the plate upright in the iodine chamber, and then cover the chamber again.</div>
		</li>
		<li data-sub-note-item="1-28">
		<div class="lab-step">Wait 3 &#8211; 4 min for the iodine vapor to stay in the spots. Then, retrieve the plate with tweezers, close the chamber, and outline the brown and yellow spots on the plate. These spots will fade, so mark them quickly.</div>
		</li>
		<li data-sub-note-item="1-29">
		<div class="lab-step">Visualize the dry 60/40 plate under UV light and then with iodine vapor in the same way.<strong> Note: </strong>To avoid side reactions, always check plates under UV light before exposing them to iodine.</div>
		</li>
		<li data-sub-note-item="1-30">
		<div class="lab-step">Now, precisely copy the spots and the solvent fronts onto the corresponding drawings of the plates in your lab notebook. For each plate, measure and record the height of the solvent front relative to the starting line.</div>
		</li>
		<li data-sub-note-item="1-31">
		<div class="lab-step">Lastly, measure the distance between the center of each spot and its starting line, and record it in your lab notebook. You can now move on to the next part of the lab.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Unknown Compound Identification<button class="expand">Expand</button>
	<p>In the second half of the lab, you&#39;ll use TLC to find out what&#39;s in an unknown analgesic. It could contain one or more of these compounds: aspirin, caffeine, and acetaminophen. These compounds are highly polar, so you&#39;ll use a premade mixture of 90% ethyl acetate and 10% hexane as the eluent.</p>
	<p>You&#39;ll run the three reference compounds and the unknown all on the same plate. Later, you&#39;ll use the Rf values of the reference compounds to identify the unknown. First, double-check which unknown material you were assigned to analyze before starting.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-3">
		<div class="lab-step">Now, lay a clean paper towel in the hood and obtain a new TLC plate. Prepare the top mark and the starting line the same way as before. Make four evenly spaced ticks on the plate, making sure that the outer marks are at least 0.5 cm away from the edges.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Draw an exact copy of the plate in your lab notebook and label the tick marks as &#8216;aspirin&#8217;, &#8216;acetaminophen&#8217;, &#8216;caffeine&#8217;, and &#8216;unknown&#8217;.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Now, bring your plate to the common bench. Spot solutions of aspirin, acetaminophen, caffeine, and the unknown that you were assigned on the appropriate marks using a clean capillary for each solution. <strong>Note: </strong>When you are spotting the unknown solution, don&#39;t dip the capillary too far into the solution vial to avoid clogging your capillary with insoluble material from the unknown substance.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Discard the capillaries and close the vials before bringing the plate back to your fume hood. Place the plate on a paper towel to finish drying.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Next, label a clean 50-mL screw-top jar &#8216;90% ethyl acetate, 10% hexane&#8217;, and bring it in a clean graduated cylinder to the solvent hood.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Place 2 &#8211; 3 mL of the 90/10 solution in the jar and return to your fume hood. Confirm that the solvent level will be below the spots on the plate. Then, place a clean filter paper upright in the jar and close it tightly.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Once the TLC plate is dry and the filter paper is saturated, carefully place the plate in the solvent. <strong>Note:</strong> It&#39;s essential to hold the plate level when you do this. If the solvent front is diagonal, the solvent distance traveled will be different for each spot, making it impossible to visually compare the unknown to the reference spots.</div>
		</li>
		<li data-sub-note-item="2-10">
		<div class="lab-step">Wait for the solvent front to reach 1 cm from the top of the plate. Then, retrieve the plate, mark it solvent front, and let it dry while lying flat.</div>
		</li>
		<li data-sub-note-item="2-11">
		<div class="lab-step">Once the plate is dry, visualize it with UV light and in the iodine chamber, and outline the spots in pencil.</div>
		</li>
		<li data-sub-note-item="2-12">
		<div class="lab-step">The unknown material could be a mixture of compounds, so look carefully for spots in line with all three reference spots.</div>
		</li>
		<li data-sub-note-item="2-13">
		<div class="lab-step">Then, precisely copy the spots onto the drawing of the plate in your lab notebook. Measure and record the height of the solvent front and the spots relative to the starting line.</div>
		</li>
		<li data-sub-note-item="2-14">
		<div class="lab-step">When you are finished, retrieve the solvent-saturated filter papers from the jars and let them dry in the hood.</div>
		</li>
		<li data-sub-note-item="2-15">
		<div class="lab-step">Pour leftover solvents into the standard organic waste, wash your glassware following your lab&#39;s usual methods, and put away your lab equipment.</div>
		</li>
		<li data-sub-note-item="2-16">
		<div class="lab-step">Throw out used TLC plates in the lab trash or with glass waste, depending on the backing material.</div>
		</li>
		<li data-sub-note-item="2-17">
		<div class="lab-step">Lastly, once the filters are dry, throw them out along with any remaining trash.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="3" data-parent-collapse="">Results<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="3-1">
		<div class="lab-step">Calculate the R<sub>f</sub> values for phenol, benzoic acid, and butyl phenyl ether eluted with 100% hexane. For each compound on the TLC plate, measure the distance from the starting line to the center of its spot. Then, divide this value by the distance from the starting line to the solvent front.</div>
		</li>
		<li data-sub-note-item="3-2">
		<div class="lab-step">Only butyl phenyl ether moved a measurable distance from the starting line, which is consistent with it being the least polar. For effective separation, the R<sub>f</sub> values should differ by 0.3 &#8211; 0.7. Thus, we can infer that phenol and benzoic acid are too polar to be separated effectively by an apolar solvent like pure hexane.</div>
		</li>
		<li data-sub-note-item="3-3">
		<div class="lab-step">Calculate the R<sub>f</sub> values for the plate that you ran in a 60/40 mixture of hexane and ethyl acetate. Ethyl acetate is a moderately polar solvent, so the compounds traveled farther and are spaced farther apart on the plate.</div>
		</li>
		<li data-sub-note-item="3-4">
		<div class="lab-step">The separation order shows that benzoic acid, the most polar compound, had the highest affinity for silica gel, whereas butyl phenyl ether, the least polar compound, had the lowest affinity for silica gel. This is consistent with the assumption that less polar compounds travel farther on polar stationary phases.</div>
		</li>
		<li data-sub-note-item="3-5">
		<div class="lab-step">Look at your third plate and calculate the R<sub>f</sub> values for aspirin, acetaminophen, and caffeine. Caffeine, the most polar complex of the three, traveled the least. Acetaminophen traveled the second farthest, while aspirin, the least polar, traveled the most.</div>
		</li>
		<li data-sub-note-item="3-6">
		<div class="lab-step">Finally, identify the compounds in your unknown material by comparing its spot or spots to the three reference spots.</div>
		</li>
	</ul>
	</li>
</ol>

Thin-Layer Chromatography: Experimental Setup and Separation - Procedure

كروماتوغرافيا طبقة رقيقة

Source: Lara Al Hariri and&#160;Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA

	Effects of Mobile Phase Composition on Compound ...

Lab Techniques

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse=""><strong>Determining the Density of an Egg</strong><button class="expand">Expand</button>
	<p>Density is a measure of how compact a substance or object is, and it is calculated as mass divided by volume. When a dense object is placed in a liquid with a lower density, the object sinks; when the object is less dense than the liquid, it floats. When the densities are the same, the object will be suspended in the liquid. In this experiment, we&#39;ll determine the density of an egg by creating a solution with the same density. We&#39;ll measure the density of the salt solution using different volume measurement glassware and determine which is the most accurate.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-1">
		<div class="lab-step">To begin, wear the appropriate personal protective equipment, including close-toed shoes, long pants, long-sleeved shirt, lab coat, chemical splash goggles, and gloves.</div>
		</li>
		<li data-sub-note-item="1-2">
		<div class="lab-step">Measure the mass of the egg. Set a weigh boat on the balance and tare it. Carefully set the egg in the weigh boat while you record the mass in your notebook.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Prepare the salt solution that will be used to suspend your egg. Use the 600-mL beaker and fill it 3/4 of the way full with deionized water.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Gently place your egg in the beaker, and then add about one teaspoon of NaCl into the water. Stir the solution gently until the NaCl dissolves. Continue to add NaCl until the egg floats just below the surface.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Use different glassware to measure the volume of the salt solution. Weigh the 50-mL graduated cylinder on the top loading balance and record the mass. Then, measure 20 mL of your salt solution and record the volume in your notebook. <strong>Note: </strong>Place a blank sheet of paper behind the graduated cylinder to read the volume more clearly. Always view the measurement at eye level and measure the volume from the bottom of the meniscus. The lines on the graduated cylinder are 0.2 mL apart, meaning that you can read the volume to the hundredths place.
		<h4><b>Table 1: Measuring Mass</b></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td style="text-align: center;"><strong>Container</strong></td>
					<td style="text-align: center;"><strong>Mass of empty container (g)</strong></td>
					<td style="text-align: center;"><strong>Mass of full containter (g)</strong></td>
					<td style="text-align: center;"><strong>Mass of solution (g)</strong></td>
					<td style="text-align: center;"><strong>Percent error</strong></td>
				</tr>
				<tr>
					<td>50-mL graduated cylinder</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>10-mL volumetric pipette</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>50-mL beaker</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>20-mL volumetric flask</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/41/Table_1._Measuring_Mass.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Weigh the filled graduated cylinder and record the mass in your notebook. Then, pour the salt solution back into the 600-mL beaker.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Use the volumetric pipette to measure volume. First, weigh the empty 50-mL beaker and record the mass in your notebook. Then, carefully measure 10 mL of the salt solution using the volumetric pipette and dispense the salt solution into the beaker.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Measure another 10 mL and add it to the beaker. Weigh the filled beaker and record the mass in your notebook. Then, empty, rinse, and dry the beaker.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Use the volumetric flask to measure volume. Weigh the empty 20-mL volumetric flask and record the mass. Then, carefully fill the flask with the salt solution to just below the 20-mL fill mark. Do not fill it all the way. Use an eyedropper to finish filling the flask so that the bottom of the meniscus just touches the fill line on the neck of the flask. Then, weigh the full flask and record the weight.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Lastly, use the 50-mL beaker to measure volume. Weigh the empty beaker, then fill the beaker with salt solution to the 20-mL line and weigh the full beaker. Record the masses in your notebook.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Measure the displacement of the egg when it is submerged in the salt solution. First, remove the egg and look at the level of the salt solution in the 600-mL beaker. <strong>Note:</strong> If it is not at a marked line, add deionized water to the solution so that the meniscus is at a readable volume and record the volume.&#160;
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td><strong>Measurements</strong></td>
					<td><strong>Salt solution using 20-mL volumetric flask&#160;</strong></td>
					<td><strong>Egg</strong></td>
				</tr>
				<tr>
					<td>Mass (g)</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Displacement of water (cm)</td>
					<td style="text-align: center;">-</td>
					<td></td>
				</tr>
				<tr>
					<td>Inner diameter of 600-mL beaker (cm)</td>
					<td style="text-align: center;">-</td>
					<td></td>
				</tr>
				<tr>
					<td>Volume (cm&#179;)</td>
					<td style="text-align: center;">-</td>
					<td></td>
				</tr>
				<tr>
					<td>Volume (mL)</td>
					<td style="text-align: center;">20</td>
					<td></td>
				</tr>
				<tr>
					<td>Density (g/mL)</td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<strong><a href="https://www.jove.com/CDNSource/lm/labs/41/Table_2._Measuring_Density.xlsx" target="_blank">Click Here to download Table 2</a> </strong></div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Gently place the egg in the beaker.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Use a ruler to measure the new height of the solution level and record the height. Then, place the ruler across the top of the beaker to measure the inner diameter.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Calculate the new volume from these measurements. Subtract the initial volume to obtain the displacement of the egg (volume).</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">To clean up from the experiment, return the egg to your instructor and pour the salt solution down the sink. Rinse all used glassware with tap water and set them out to dry. Finally, return the sodium chloride to your instructor.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse=""><strong>Results</strong><button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="2-1">
		<div class="lab-step">Calculate the mass of the solution in each of the different volumetric glassware by subtracting the empty glassware mass from the full glassware mass.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Keep track of uncertainty in your measurement by using significant figures. For example, when we look at the graduated cylinder measurement, the weight of the empty container is 90.92, and the weight of the full container is 111.59. The weight measurements have significant figures to the hundredths place, so it is important that significant figures are maintained throughout our calculations. Thus, the mass of the 20-mL salt solution is 20.67 g.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">The 50-mL beaker weighed 28.65 g when it was empty and 47.96 g when it contained 20 mL of salt solution. Therefore, the mass of 20 mL of the salt solution is 19.31 g.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Repeat the calculation to obtain the mass of 20 mL of salt solution that was measured using the 10-mL pipette and the 200-mL volumetric flask.<b> Note:</b> Generally speaking, volumetric measurements are more accurate when using a volumetric flask.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Look at the accuracy of the other methods compared to the volumetric flask in terms of percent error. Percent error is calculated by subtracting the theoretical value from the experimental value, then dividing by the theoretical value times 100.
		<ul>
			<li><img src="https://www.jove.com/CDNSource/lm/labs/41/41_Procedure_1b.jpg" /></li>
		</ul>
		</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Use the volumetric flask measurement as the theoretical value to determine the percent error for the other volume measurement methods. As expected, the volume measurement that uses the markings on the beaker is the least accurate.<strong> Note: </strong>We also know this because the known density of pure water is 1 g/mL. Thus, 20 mL of pure water weighs 20 g. The density of the salt solution must be higher than 20 g since salt was added to the water.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Calculate the density of the salt solution using the volumetric flask measurement. Divide the mass of the solution by the volume of the solution. Thus, the density of the salt solution is 1.053 g/mL.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Compare the calculated density of the salt solution to the density of the egg. The volume calculated using the displacement of water in a beaker was found to be 61.14 cm<sup>3</sup> or 61.14 mL. The weight of the egg was measured to be 60.15 g, so its density is 0.9838 g/mL. The disparity between the density of the egg and the density of the salt solution arises from error introduced in both calculations, primarily due to volume measurement readings.</div>
		</li>
	</ul>
	</li>
</ol>

Accuracy, Precision, Uncertainty, and Significant Figures - Procedure

تقنيات المختبر

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Determining the Density of an EggExpand
	Density is a measure of how compact a substance or ...

Cell Structure

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Visualizing Onion and Human Cells
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">In this experiment you will prepare different types of cells from a plant and animal, onion and human respectively, and then visualize them under a microscope. HYPOTHESES: The experimental hypothesis is that the cells will appear different in overall shape and membrane structure, but there will be some shared similar structures, like nuclei, in both cells. The null hypothesis of the experiment is that there will be no difference in structure between the two cell types.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">First, to prepare an animal cell slide, start by pouring 30 mL of distilled water into a beaker.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Then, use a glass dropper to place 2 - 3 drops of the water onto the center of a clean microscope slide.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Next, take a clean toothpick and scrape the inside of your cheek to gather cells.  CAUTION: Do not scrape your cheeks too aggressively. The scraping should not cause discomfort or bleeding. 
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Put the end of the toothpick with the cheek cells onto the wetted area of the slide and mix the water and cheek cells together.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">Next, add two drops of methylene blue staining solution to the wetted area of the slide and mix it in with a clean toothpick.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Let the mixture sit at room temperature for 3 minutes.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">After 3 minutes have passed, use a glass dropper to add a drop of glycerol to the mixture.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Carefully, place a cover slip over the mix on the slide by first standing one end of the cover slip vertically and aligning it along to one side of the mixture. Then, carefully lower the other end of the cover slip down until the mixture is completely covered.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Finally, remove any excess liquid with blotting paper.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">Next, prepare a slide of plant cells by placing five drops of distilled water into a clean watch glass.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Then, with forceps, take a thin strip of onion and place it into the water.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Apply 5 drops of safranin solution to another watch glass.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Now using a pair of forceps transfer the piece of onion from the distilled water into the safranin.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Allow the onion to soak for 30 seconds.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Then, again with forceps, move the onion back into the distilled water.
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Now, place 3 drops of glycerol onto the center of a glass microscope slide.
</div></li><li data-sub-note-item="1-18"><div class="lab-step">Using the forceps again, transfer the onion into the glycerol on the slide.
</div></li><li data-sub-note-item="1-19"><div class="lab-step">Gently place a cover slip over the onion on the slide and blot away any excess liquid with a piece of blotting paper.
</div></li><li data-sub-note-item="1-20"><div class="lab-step">Next, you will visualize the slides you have prepared using a compound microscope. First, turn on the scope and set the objective lens to the lowest level of magnification.  NOTE: A compound microscope typically has two levels of magnification.
</div></li><li data-sub-note-item="1-21"><div class="lab-step">Place the cheek tissue slide onto the stage of the microscope and bring the cells into focus by adjusting the stage and using the coarse adjustment knob.
</div></li><li data-sub-note-item="1-22"><div class="lab-step">When the cells are in focus, observe the individual cells and draw what you see. Repeat these observations at medium and high magnifications adjusting the focus with the fine adjustment knob. IMPORTANT: Do NOT use the coarse adjustment knob at high magnifications. 
</div></li><li data-sub-note-item="1-23"><div class="lab-step">Next, rotate the nose piece so that the oil lens is almost in place.
</div></li><li data-sub-note-item="1-24"><div class="lab-step">Place a drop of immersion oil on top of the cover slip of the cheek cell slide.
</div></li><li data-sub-note-item="1-25"><div class="lab-step">Use the oil lens to view the cheek cells and record your observations.
</div></li><li data-sub-note-item="1-26"><div class="lab-step">Repeat these steps to view the onion plant cell, moving again from low to medium, high, and oil lenses (steps 20 &#8211; 24).
</div></li><li data-sub-note-item="1-27"><div class="lab-step">Record all of your observations and note the differences you see between animal and plant cells.
</div></li><li data-sub-note-item="1-28"><div class="lab-step">When you are finished, place the cheek cell slide and toothpicks into a diluted bleach solution. Dispose of the cover slips into a glass waste container.
</div></li><li data-sub-note-item="1-29"><div class="lab-step">Finally, turn off the microscope and clean the lenses with lens cleaning paper.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">Calculate the total magnification for each of the viewing levels. Remember to account for both the eyepiece magnification and the objective lens magnification. NOTE: Eye piece: 10X magnification, Objective lens: 4X, 10X, and 40X magnification
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Then, identify the structural differences between plant and animal cells using the observations made under the microscope.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Label the nuclei in both cell types and then highlight or note any differences that you see between them.
</div></li></ul></li></ol>

Cell Structure: Visualizing Onion and Human Cells - Procedure

هيكل الخلية

Visualizing Onion and Human Cells
ExpandIn this experiment you will prepare different types of cells from a plant and animal, onion and human ...

Biology

Fundamentals

Diffusion and Osmosis

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Diffusion in Agar
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">NOTE: In this exercise, you will be given agar containing an indicator chemical called phenolphthalein. When phenolphthalein is exposed to the normal alkaline conditions in the agar, it will look pink. But when it is exposed to neutral or acidic conditions, it changes from pink to clear. You will make different size and shaped agar cubes as a model for cells to study the impact of cell size and shape on diffusion rate.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">To make the first set of cells, measure out and cut a small cube of agar where each side measures one centimeter. 
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Next, measure and cut out a medium cell cube with sides of 2 cm and a large cell of 3 cm on each side.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Knowing the length of the sides of your cube cells, calculate their surface area using this equation, where lower case a represents the length of the sides: Surface Area = 6a^2
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Record these values in the appropriate column in Table 1. <a href="https://www.jove.com/CDNSource/lm/labs/6/Table_1_Diffusion_and_Osmosis.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 1</a>
</div></li><li data-sub-note-item="1-6"><div class="lab-step">Then, use the same length value and the equation below to calculate the volume of each cube and add these to the table: Volume = a^3 HYPOTHESES: The experimental hypothesis might be that the acid will diffuse completely to the center of the small cell faster than the medium and large cells. The null hypothesis could be that the acid will diffuse to the center of the small and two larger cubes at around the same time.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Add 100 mL of 0.1 M HCl to each of the three 400 mL beakers to make the diffusion baths.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">Working in a team, have one experimenter ready with the timer and the second and third experimenters ready to drop each cube into one of the beakers.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">When the first experimenter says go, simultaneously drop all three cubes into their respective beakers and start the timer.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Observe carefully until one of the cubes becomes completely clear or 10 min have passed.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">Stop the timer, remove the agar cubes from the beakers and place the cubes into a Petri dish.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Make a note of which of the three cells became clear or had the smallest remaining pink area. Then, also note which cell had the most remaining pink agar.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Next, in Table 1, calculate the surface area to volume ratio for each cell. Surface Area: Volume Ratio = (surface area)/volume
</div></li><li data-sub-note-item="1-14"><div class="lab-step">As the cell size increases, note whether the surface area to volume ratio increases or decreases. Also consider whether this correlates with your observation of the depth of diffusion into the agar cells. If cells rely on diffusion to deliver essential nutrients and molecules to the whole cell, discuss with your group if it would be better to have a smaller or larger surface area to volume.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Now, with the remaining agar, cut three rectangular shaped blocks of different sizes and record their length, width, and height. This will test what happens when the shapes of cells are different. 
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Calculate the surface area of your rectangular cells using the formula below, where length is l, width is w, and height is h. Surface Area = 2lw + 2lh + 2wh
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Then, calculate the volume of your rectangles using this formula: Volume = l * w * h
</div></li><li data-sub-note-item="1-18"><div class="lab-step">Repeat the experiment by dropping the new shapes into the hydrochloric acid solution for 10 min or until one cube becomes completely clear.
</div></li><li data-sub-note-item="1-19"><div class="lab-step">Remove the cell shapes from the solutions and observe the depth that the hydrochloric acid diffused into each of these cells, and which shapes have the smallest and largest remaining pink areas not reached by the solute.
</div></li><li data-sub-note-item="1-20"><div class="lab-step">Using the surface area and volume data you recorded for your rectangular shapes, calculate the surface area to volume ratio of these cells. Surface Area: Volume Ratio = (surface area)/volume
</div></li><li data-sub-note-item="1-21"><div class="lab-step">Consider whether these values correlate to which cells had the most and least complete diffusion. Additionally, discuss with the group whether these rectangular cells displayed a similar or different pattern of diffusion to that observed with the cube shaped cells, and what this might mean.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Movement of Molecules Across a Semi-Permeable Membrane
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">Before beginning the experiment, add 250 mL of distilled water to each of four 1 L beakers.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Then, label the beakers from 1-4, and add 0.5 mL of iodine to the first beaker. HYPOTHESES: In this experiment, the experimental hypothesis is that some of the solutes will be able to pass through the dialysis tubing membrane and others will not. The null hypothesis is that there will be no difference in the ability to diffuse through the dialysis tubing membrane between the solutes.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">To prepare the dialysis tubing, remove the pieces one at a time from the distilled water bath and tie a tight knot at one end of each tube. These tubes, when filled, will act as model cells with the dialysis tubing acting like the semipermeable membrane.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">Add 10 mL of starch solution to the first tube and tie off the open end, making sure to leave space in case the tubing expands during the experiment.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">Then add 10 mL of the NaCl and dextrose solutions to the second and third pieces of tubing, respectively, and tie off both tubes, again, leaving space in case of expansion.
</div></li><li data-sub-note-item="2-6"><div class="lab-step">After adding 10 mL of distilled water and tying off the fourth tube, weigh each of your model cells.
</div></li><li data-sub-note-item="2-7"><div class="lab-step">Record the initial weight values in grams and the colors of the starting solution in each tube in the appropriate columns of Table 2. <a href="https://www.jove.com/CDNSource/lm/labs/6/Table_2_Diffusion_and_Osmosis.xlsx" target="__blank" style="display:block;margin:20px;">Click Here to download Table 2</a>
</div></li><li data-sub-note-item="2-8"><div class="lab-step">After quickly rinsing the outside with tap water, place each piece of tubing in its corresponding beaker for 1 h at room temperature. NOTE: For example, the starch solution tube should be placed into the beaker containing the iodine.
</div></li><li data-sub-note-item="2-9"><div class="lab-step">At the end of the diffusion period, weigh the tubes again.
</div></li><li data-sub-note-item="2-10"><div class="lab-step">Then, observe the tubes carefully, noting any color changes. 
</div></li><li data-sub-note-item="2-11"><div class="lab-step">Record all of these data in Table 2. 
</div></li><li data-sub-note-item="2-12"><div class="lab-step">Next, to perform a Benedict&#39;s Reagent test for simple sugars, make a water bath by adding 250 mL of water to a 600 mL beaker and placing it onto a hot plate.
</div></li><li data-sub-note-item="2-13"><div class="lab-step">Set the plate to high, to boil the water. 
</div></li><li data-sub-note-item="2-14"><div class="lab-step">Label two new glass test tubes as H<sub>2</sub>O and dextrose, respectively.
</div></li><li data-sub-note-item="2-15"><div class="lab-step">Use a graduated cylinder to transfer 1 mL of solution from the water and dextrose beakers into the corresponding test tubes.
</div></li><li data-sub-note-item="2-16"><div class="lab-step">Then, add 2 mL of Benedict&#39;s Reagent to each tube. 
</div></li><li data-sub-note-item="2-17"><div class="lab-step">Once the water is boiling, place each test tube into the water bath for 3-5 minutes.
</div></li><li data-sub-note-item="2-18"><div class="lab-step">After this time, note the color of the solution in each tube. 
</div></li><li data-sub-note-item="2-19"><div class="lab-step">Then use this key to assess whether the test is positive or negative and record these data in the appropriate column in Table 2. <a href="https://www.jove.com/CDNSource/lm/labs/6/Lab_6_Diffusion_Figure_1.png" style="display:block;margin:20px;" target="__blank">Click Here to download Figure 1</a>
</div></li></ul></li><li data-note-item="3" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="3-1"><div class="lab-step">First, look at the mass of your four dialysis tube cells at the beginning versus the end of the experiment. Calculate the change in mass for each of the four cells and plot it onto a bar chart.
</div></li><li data-sub-note-item="3-2"><div class="lab-step">Note which cells demonstrated the most change, and whether any of the cells appeared visibly different in size.
</div></li><li data-sub-note-item="3-3"><div class="lab-step">For the experiment with the starch and iodine indicator, note whether there was a color change in the fluid in the artificial cell. Also consider whether there was a color change in the water in the beaker, and what both of these observations say about the properties of the dialysis tubing membrane.
</div></li><li data-sub-note-item="3-4"><div class="lab-step">Finally, in the Benedict&#39;s Reagent test for dextrose, note whether this simple sugar was able to pass through the semipermeable membrane of the &#8220;cell&#8221; into the water in the beaker. Discuss with the class which of the molecules you think could and could not pass through the semipermeable membrane.
</div></li></ul></li></ol>

الانتشار والتناضح

Diffusion in Agar
ExpandNOTE: In this exercise, you will be given agar containing an indicator chemical called phenolphthalein. When phenolphthalein is ...

Physiology of the Circulatory System

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Measuring Circulatory System Function in Humans
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">Before starting the experiment go to the front of the room and collect an alcohol swab, a sphygmomanometer, and a stethoscope.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">Clean the earpieces with the alcohol swab and then insert them into your ears.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">To check if the stethoscope is in the on position, gently tap the flat metal disc called the diaphragm.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">If you hear a sound it&#39;s on. If not, turn the metal disc and tap again and keep turning and tapping the disc until you hear a sound. NOTE: For this experiment you will work in pairs. One person will measure their partner&#39;s blood pressure, while the person being measured will count their heartbeats over the course of one minute.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Fill out table one with the name of the person being monitored. HYPOTHESES: The experimental hypothesis is that systolic blood pressure will be higher when the person is sitting when compared to lying down because more pressure is required for blood to be moved around the body. The null hypothesis is that there will be no difference in systolic blood pressure whether a person is sitting or lying down.<a href="https://www.jove.com/CDNSource/lm/labs/9/Table_1_Physiology_of_Circulatory_System.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 1</a>
</div></li><li data-sub-note-item="1-6"><div class="lab-step">The person being monitored should begin by lying down. Next, they will need to locate their pulse by placing two fingers next to their windpipe. If a throbbing sensation is felt, this is the pulse.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Now, ready a time keeping device to count out 1 minute as the person taking their pulse will be having their blood pressure taken at the same time.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">At this point, the person measuring blood pressure should place the cuff of the sphygmomanometer around the other arm of the subject and the stethoscope earpieces into their own ears.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Start the timer.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">The person being monitored should begin counting the number of heartbeats felt over one full minute. While the subject is taking their pulse, the person taking blood pressure should place the diaphragm of the stethoscope under the cuff on the inside of their partner&#39;s elbow.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">Then, pump the cuff to 200 mm of mercury.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Gently and slowly twist the metal knob on the sphygmomanometer to release air from the cuff.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">As pressure is released the first Korotkoff sound should be heard. The corresponding value on the sphygmomanometer is the systolic blood pressure. Consistent sounds should be heard until they die out with the last sound signifying the diastolic blood pressure.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Record the systolic pressure, the diastolic pressure, and the heart rate in Table 1.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Now, repeat the blood pressure and pulse measurements with each partner keeping the same role but this time the subject should be sitting upright.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Record these data in the appropriate places in Table 1.
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Finally, the partners should switch spots. So now, the person measuring blood pressure should be taking their pulse and acting as the subject.  NOTE: Be sure to wipe the earpieces of the stethoscope between users and don&#39;t forget to record your measurements in Table 1.
</div></li><li data-sub-note-item="1-18"><div class="lab-step">After finishing the experiment, discard all alcohol swabs into the trash. Then, bring the sphygmomanometer and stethoscope back to the front of the room.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Measuring Respiratory Rate in Fish
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">To prepare for this second experiment, collect two clear containers.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Begin by filling half of one container with aquarium water.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Then, use a fish net to gently catch a goldfish and place it into the cup. Pinch the net around the fish or else it may jump out of the net.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">Familiarize yourself with the operculum of the fish. The operculum covers the gills and it is located behind and below the eye. When the fish respires the operculum moves in and out and this is one gill beat. HYPOTHESES: In this experiment you will measure the gill beats of the fish in different water temperatures. The hypothesis is that there will be a significant correlation between the temperature and respiration rate in goldfish. The null hypothesis is that there will be no correlation between temperature and respiration rate.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">Take the other empty container with a screw cap, the cup with your fish, and the net to the water tanks.
</div></li><li data-sub-note-item="2-6"><div class="lab-step">Then, fill the empty container with the water from the lowest temperature water bath. This will act as your first respiration rate chamber.
</div></li><li data-sub-note-item="2-7"><div class="lab-step">Next, hold the fish net over a wastewater container and dump out the water from the cup holding the fish so that the fish falls into the net. Pinch the net around the fish without touching the fish itself.
</div></li><li data-sub-note-item="2-8"><div class="lab-step">Bring the net over the top of the container with the bath water and let go of the net to release the fish into the vial.
</div></li><li data-sub-note-item="2-9"><div class="lab-step">Once the fish is in the container, submerge it back into the water bath and then screw the cap on to prevent outside oxygen from entering the vial.
</div></li><li data-sub-note-item="2-10"><div class="lab-step">Next, remove the container from the controlled temperature water bath and place it on your workbench surface to avoid warming the water with body heat.
</div></li><li data-sub-note-item="2-11"><div class="lab-step">One partner should immediately begin counting the gill beats as soon as the second partner starts the stopwatch.
</div></li><li data-sub-note-item="2-12"><div class="lab-step">Continue counting the beats for 20 seconds. Record the number of beats in column A of Table 2. <a href="https://www.jove.com/CDNSource/lm/labs/9/Table_2_Physiology_of_Circulatory_System.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 2</a>
</div></li><li data-sub-note-item="2-13"><div class="lab-step">Repeat the measurement one more time and record the number in column B.
</div></li><li data-sub-note-item="2-14"><div class="lab-step">Next, hold the fish net over a wastewater container and dump out the water from the fish vial so that the fish falls into the net.  IMPORTANT: Move from lowest to highest temperature, so the fish is not stressed between trials.
</div></li><li data-sub-note-item="2-15"><div class="lab-step">Repeat the experiment for the remaining four temperature conditions (steps 8 &#8211; 13).
</div></li><li data-sub-note-item="2-16"><div class="lab-step">Record all the values for different temperatures in Table 2.
</div></li><li data-sub-note-item="2-17"><div class="lab-step">Once you are done, slowly mix water from the last respiration chamber with the fish tank water and then return the fish to the home tank. NOTE: This should be done over the course of approximately 10 minutes.
</div></li></ul></li><li data-note-item="3" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="3-1"><div class="lab-step">It&#39;s time to analyze the data that you just collected. Look at the blood pressure and heart rate measurements for the different trials. If they were different, make a hypothesis to explain your observations. 
</div></li><li data-sub-note-item="3-2"><div class="lab-step">For the gill beat experiment, average the numbers in columns A and B and calculate the fish respiration rate as gill beats per minute.
</div></li><li data-sub-note-item="3-3"><div class="lab-step">Next, plot the graph of temperature versus gill beats per minute.
</div></li><li data-sub-note-item="3-4"><div class="lab-step">Record any correlations you see between the variables. If a correlation is observed, determine if it is positive or negative and provide an explanation for this result.  NOTE: Consider the fact that fishes are ectotherms and the impact of temperature on dissolved oxygen.
</div></li></ul></li></ol>

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