Name: experimental procedure for warm spinning of cast aluminum components
Uploaded: 2017-02-01T15:00:00.000+00:00
Duration: 7 min 36 s
Description: Watch this Scientific Journal Video about Experimental Procedure for Warm Spinning of Cast Aluminum Components at JoVE.com

<p class="jove_content">作者要感谢罗斯麦克劳德，空间DavidTörök，Wonsang Kim和吴嘉龙对他们的技术支持。 MJ罗伊要感谢苛刻环境中心博士培训和力拓加铝为通过研究奖学金奖励资金支持EPSRC（EP / L01680X / 1）通过材料的支持。 </p>

<p class="jove_title"> 1.工件准备成型试验</p><ol><li>获得加工心轴尺寸，使得内径跳动为0.2mm铸态的工件，而外径保持尽可能多的铸态表面越好。 <br />注意:如果坯料从全尺寸轮铸件拉伸，加工操作是必需的以除去所有毂和辐条部，同时提供可使用的夹紧工件心轴的功能。这包括去除在板法兰。 </li><li>预加热能够接收整个工件至135℃，清洗，在炉脱脂和地点工件为一小时，以热障涂层的应用程序编写一个棺材炉。 </li><li>迅速除去从炉工件，并放置在涂层夹具。使用汽车型喷涂机，应用热障模涂一薄层的内径。 <br />注:该涂料将提供润滑，减少热传递到成形操作过程中的心轴上。 </li></ol><p class="jove_title"> 2.工装准备</p><ol><li>擦拭芯棒表面用湿布。确保该芯棒具有利用沿成形长度千分表指示器&lt;0.5mm的总的旋转的跳动。与从事尾座板现场加工中心评估这一点。使用扭矩扳手，确保那些对合模组件抛开所有紧固件是否拧紧到规定的扭矩值12.9级螺栓（单位Nm:M8  -  40，M12  -  135，M16  -  340）。 </li><li>由第一供电的气体供给螺线管，然后点燃用火石火炬点火器启动预加热系统。运行10分钟，以排出在火炬/软管收集的任何冷凝物预热系统。通过停用供气电磁熄灭。 </li><li>与干600 / P1200粒度的金刚砂纸芯轴删除任何松动/氧化涂层，同时以每分钟20转转动芯棒（RPM）。 </li><li>功率板载数据采集模块，并运行该预加热系统，直到嵌入在芯棒表面上的热电偶读取200℃与活顶尖啮合。 </li><li>使用汽车型喷涂机，轻轻涂上一种水基锻造润滑剂芯棒表面，并允许该旋转模具冷却至环境温度与即时工具中心接合。 </li><li>松开滚轮架（ <strong>图3）</strong>用扳手锁紧螺母装配。设置使用工具制造者的量角器辊组件的方法或攻角，并拧紧内部和外部螺母（M35  -  750牛米）。 </li><li>首先接合M12肩螺栓元件2连接到安装支架组装3钳总成（ <strong>图4）。</strong>检查任何热变形，这将阻止元件2 <strong>图4</strong>从对夹紧托架平稳运行。确保他们自由移动，轻轻ş安定干320 / P400粒度碳化硅纸接触表面。根据需要，用布应用高温基于钼的润滑剂的薄层。 </li></ol><p class="jove_title"> 3.成型操作</p><ol><li>移动辊工具站在离朝主轴心轴完全离开，将尾座和中心明确芯棒。工件手动滑到芯轴确保即使参与。 <br />注:由于毛坯名义上对称，没有首选方向。 </li><li>通过接合锥形模销和手拧紧穿过心轴插入夹块运行M16螺栓装配夹具到心轴上。确保有通过旋转和手动收紧施加均匀的压力，随后是气动冲击扳手设置为50牛顿米。 </li><li>启动加热系统并立即开始心轴以20rpm旋转。保持施加热，直到夹子松动。所考虑的过程，这是AP近因3分钟。 <br />注:这一次将是每个工件略有不同，由于在工件/芯棒装修细微的差别。 </li><li>熄灭加热系统并停止心轴这样的旋转，该第一夹持是用冲击扳手访问。在30秒内，拧紧用冲击或手动扳手所有夹钳并记录工件的表面温度在沿所述成形区域的长度与簧片型热电偶探头3的位置。 </li><li>重复步骤3.4至工件在适当的成形温度;在最低限度，350℃为A356。用扳手设置为200 Nm的执行夹子的最终拧紧。 </li><li>轴向和径向移动至辊子（约从工件表面2-5毫米）到用于形成位置，并执行最后一个夹具紧固（ <em>即</em>步骤3.4）。 </li><li>与上，增加了车床到预期的形成速度的旋转速度加热系统，接合辊预先设定的深度进入工件，并激活螺纹切削进给沿工件的长度轴向移动辊。 <br />注:对于目前的几何形状，合理的结果达到281转0.21毫米/转的轴向运动。 </li><li>重复步骤3.7根据需要，增加变形的水平。各自形成通后，确保温度不通过停止心轴和如在步骤3.4采用使用相同的簧片型热电偶探头下降的最优形成温度以下。如果最佳成形温度有所下降，重复步骤3.4和3.5重新加热。 <br />注:加热炉可以采用，但在可能达到的夹紧系统的抑制工件能力的程度为代价。 </li></ol><p class="jove_title"> 4.后成型操作</p><ol><li>一旦获得变形的所需的水平时，停止加热系统，和撤消所有夹具，和脱离尾座以获得第一百arance工件删除。 </li><li>轻轻拍打工件用一块黄铜从芯棒分离。如果这被证明是无效的，重新接合所述加热系统和以20rpm旋转心轴轻轻拍打，直到坯件分离出来。 </li><li>使用适当的操纵工具如夹钳或重绝缘手套，或者在60℃下骤冷于水中，工件以防止进一步的老化，或离开空气冷却，以减少残余应力/变形。 </li></ol>

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<p class="jove_content">作者什么都没有透露。 </p>

<p class="jove_content">上述突出所采用的协议和设备能够形成在高温下铸铝所示的代表性结果，并提供了一个平台，以确定流形成模具轮的加工窗口。表现出的技术可以用来探索形成信封，包括如何都形成和未成形材料响应热处理<sup class="xref">8</sup>的各方面。但是，有改进的余地与该装置的当前处理的协议。 </p><p class="jove_content">关于进一步的仪器，这将加速过程模型开发，列入机床测力计和摩擦测试仪<sup class="xref"><sup><sup class="xref">11，12</sup></sup></sup>来测量形成在辊上负荷和摩擦系数将提供关于工艺条件的重要信息。这是为正交加工研究一个广泛采用的仪器技术，并且可以在当前机器上容易实现。这另外的仪器将提供有用的数据，以正确地验证建模工作<sup class="xref"><sup><sup class="xref">13,14</sup></sup></sup>和支持在此过程中，不断增加的工业利益。为了有效地捕获处理期间的坯料的温度的演变，非接触测量技术是期望的。然而，常见的基于红外的技术由铝的低发射率和如何处理期间表面的变化而受到阻碍。这是主要的原因，一个仪表，调试被采用以捕获与所描述的协议来实现的典型的热响应空白，并担任填充基线传热分析以涉及芯棒表面温度到工件上。 </p><p class="jove_content">因为它在很大程度上是一种材料的手动成形方法，该方法是敏感的时间在温度，运行之间的一些不一致运行是可以预料的。铝合金有那些对温度高于100℃，由于老化机制高度敏感的微观结构。因此，在协议中最重要的步骤是1.2和3.3-3.7，其中所述坯件是在高温下。拧紧并重新座位夹具必须尽快进行，以形成操作之间保持重复性。 </p><p class="jove_content">在预加热步骤中使用的<em>原位</em>工件加热是相当低效的，并可能通过辐射加热来提高。在的心轴和刀具运动方面的总体处理速度，可以实现被稍微所采用的车床的能力的限制。更高形成速度需要具有更高的负载能力更刚性的框架，尤其是当一个更强的材料的成形是要尝试。工件夹紧和松开可以与除液压或气动驱动的改进。如从血乳酸传热nk的心轴在很大程度上是由工件上芯棒施加的压力的函数，这另外还可以提高一个基于模型的方法与现有的系统中形成期间，以确定在工件的温度。 </p><p class="jove_content">描述的装置和过程表明，在这些条件下该材料成形载荷接近那些标准车削操作，并且仍然是一个非常符合成本效益的过程，其中以执行制造试验。研究了不同的制造路线和成形性可以从商业形成设备，这是操作非常昂贵执行程。随着设备和协议说明，加工参数可以建造更大的规模，更高的吞吐量设备之前进行调查，并以作者的知识，是一种独特的方法。 </p><p class="jove_content">随着开发的协议只被应用于铸造铝合金的一个特定变型，再是它可以用于各种超越汽车车轮的应用程序进行调查，其他铝铸造合金的多种。由于这些合金具有来自温度透视大致类似的处理窗口，开发的协议可以容易地适应。 </p>

<p class="jove_content">一位在航空和运输部门目前正在实行的更具挑战性的金属成型操作的是金属旋压，包括衍生产品如剪切成型和流动形成<sup class="xref"><sup><sup class="xref">1，2。</sup></sup></sup>在此过程中，一个轴对称的工件被放置在代表最后的所需形状的心轴，并纺成与一个或多个冲击辊子接触。工件被辊芯棒和压缩之间再塑性变形，与包括联合弯曲，细化和轴向伸长多样反应。在具有有限的延展性或以其他方式难以形成的材料时，这有时在高温下进行，以减少流动应力和增加的延展性。 </p><p class="jove_content">从处理的观点来看，也有广泛的可支配的形状和制造组件的性能的参数。许多研究都集中关于用于优化各种参数<sup class="xref"><sup><sup class="xref"><sup><sup class="xref">3，4，5</sup></sup></sup></sup></sup>的统计技术。变量包括模具的几何形状，如工具和心轴的形状;形成速度既包括芯棒旋转速度和模具的进给率;以及材料特性。当需要升高的温度，从业者需要评估，同时仍保持良好的产品所需的最低温度。 </p><p class="jove_content">铸铝合金在各种汽车和航空航天应用中采用，以在汽车轮毂的合金A356。然而，这种合金是不适合于由于其有限的延展性室温<sup class="xref"><sup><sup class="xref">6,7</sup></sup></sup>形成，并且必须在升高的温度下形成。这引入了处理的复杂性，主要是在控制温度的宿主。由于这种材料的性质改变标志意义ntly随温度<sup class="xref">8，</sup>以执行仪表化试验中，温度条件可以保持在合理的加工窗口内以及被监视它是特别重要的。上铸A356在宽范围的应变速率的范围从环境温度到500℃的热机械行为的详细数据可以在其他地方进行审查。 <sup class="xref">9</sup> </p><p class="jove_content">为了支持开发和流动形成车轮制造业务的优化，定制成型设备已经在材料工程在不列颠哥伦比亚大学（ <strong>图1）</strong>部制定。该装置已被主要由22千瓦的总输出，用82千瓦（ <strong>图2）</strong>的峰值输出丙烷喷灯加热系统手册，皮带驱动绞盘车床建造。用一个刚性辊组件沿嵌入式热电偶的芯棒（ <strong>图3）</strong>已经装，其能够形成工件高达330毫米的直径。所述心轴具有一个手工激活夹紧系统，其能够以考虑在工件直径加工（ <strong>图4）</strong>期间发生大的变化。一种电池操作的含有能形成过程中监测心轴的温度和用于表征加热坯料已安装在车床的主轴的一个微型无线计算机的数据采集系统（DAQ）。而其它流动形成工艺已被使用适于车床合成<sup class="xref"><sup><sup class="xref">4,10，</sup></sup></sup>本装置是在第一<em>原位</em>加热和热的数据采集来体现。 </p><p class="jove_content">对于工业上规模成形操作的处理协议已被开发以提供指示处理的条件。随后描述的，该协议包括模具和工件的准备，形成惯例，共同的与成形试运行结束ncluding。 </p><p class="jove_content" fo:keep-together.within-page="1"><img alt="图1" src="/files/ftp_upload/55061/55061fig1.jpg" /><br /> <strong>图1:</strong> <strong>实验仪器概述。</strong>其中已添加到修改的绞盘车床在高温下形成原理的组件。设备（顶部）和标记上的计算机辅助设计的描绘（底部）主要工作方向和元件的照片。 <a href="http://ecsource.jove.com/files/ftp_upload/55061/55061fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> </p><p class="jove_content" fo:keep-together.within-page="1"><img alt="图2" src="/files/ftp_upload/55061/55061fig2.jpg" /><br /> <strong>图2:供暖系统的细节。</strong>以丙烷加热系统从含有气体控制螺线管（顶部和底部左侧）一个中心歧管致动四个离散的燃烧器（顶部和底部右侧）。气体的压力和离散流量到每个燃烧器是可能的，与沿所述坯件放置沿着以符合不同的几何形状。 <a href="http://ecsource.jove.com/files/ftp_upload/55061/55061fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> </p><p class="jove_content" fo:keep-together.within-page="1"><img alt="图3" src="/files/ftp_upload/55061/55061fig3.jpg" /><br /> <strong>图3:</strong> <strong>滚轮架装配细节。</strong>上的车床已适于保持在任意的辊原工具夹具角相对于心轴的通过锁紧螺母组件的转动轴线。 <a href="http://ecsource.jove.com/files/ftp_upload/55061/55061fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> </p><p class="jove_content" fo:keep-together.within-page="1"><img alt="图4" src="/files/ftp_upload/55061/55061fig4.jpg" /><br /> <strong>图4:</strong> <strong&gt;仪器化芯棒和夹具系统概述。旋转工具已被设计成直接螺栓固定在车床的主轴，而这又是通过在尾座（顶部和底部左侧）一活顶尖支撑。夹持组件/动作也描绘（顶部和底部右侧）。 <a href="http://ecsource.jove.com/files/ftp_upload/55061/55061fig4large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> </p>

<table><tbody><tr><td>&lt;strong&gt;Reagent/Material&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>High temperature grease</td><td>Dow Corning</td><td>Molycote M-77</td><td></td></tr><tr><td>High temperature lubricant</td><td>Superior Graphite</td><td>sureCOAT</td><td></td></tr><tr><td>High temperature die coat</td><td>Vesuvius/Foseco</td><td>DYCOTE 32</td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Live center</td><td>Riten Industries</td><td>17124</td><td>Bell-head, spring loaded</td></tr><tr><td>Live center adapter</td><td>Riten Industries</td><td>431</td><td>Adapter for lathe</td></tr><tr><td>Impact wrench</td><td>Chicago Pneumatic</td><td>CP7749-2</td><td>1/2&quot; drive, 0-545 ft-lb</td></tr><tr><td>Torque wrench</td><td>Westward Tools</td><td>6PAG0</td><td>1/2&quot; drive, 0-250 ft-lb</td></tr><tr><td>Air-powered paint sprayer</td><td>Cambell Hausfeld</td><td>DH4200</td><td>For die coat</td></tr><tr><td>Air-powered paint sprayer</td><td>Cambell Hausfeld</td><td>DH5500</td><td>For graphite-based lubricant, high volume low pressure (HVLP) type</td></tr><tr><td>Data acquisition unit</td><td>Measurement Computing</td><td>USB-2416</td><td></td></tr><tr><td>Reed thermocouple</td><td>Omega Engineering</td><td>88108</td><td></td></tr><tr><td>Propane tank</td><td>Generic</td><td></td><td>20/40 lb, POL fitted</td></tr><tr><td>Solenoid valve</td><td>Aztec Heating</td><td>SV-S121</td><td></td></tr><tr><td>Gas regulator</td><td>Aztec Heating</td><td>67CH-743</td><td>0-30 psi</td></tr><tr><td>Burner tips</td><td>Exact</td><td>3119</td><td>Qty: 4</td></tr><tr><td>Roller bearings</td><td>SKF</td><td>32005 X/Q</td><td>Qty: 2</td></tr><tr><td>Remaining equipment designed and fabricated in-house</td><td></td><td></td><td></td></tr></tbody></table>

experimental procedure for warm spinning of cast aluminum components

<p class="jove_content">高性能，铸铝汽车轮毂被越来越多地通过逐步形成流量/金属旋压在高温下形成，以提高材料的性能。用各种各样的工艺参数可影响这两个形状实现和得到的材料性质，这种类型的处理是非常困难的佣金。这个过程的简化，轻型版本已设计和全尺寸的汽车轮毂实施。该装置的目的是帮助理解变形机制和这种类型的处理的材料的反应。一个试验性协议已经发展到准备，并随后进行成型试验和铸A356轮毛坯描述。热分布达到，连同提供仪器的信息。相似满刻度形成能赋予以更快的速率显著更变形的操作进行讨论。 </p>

<p class="jove_content" fo:keep-together.within-page="1">如铸铝A356工件是根据本文中所描述的方法形成。从铸轮采用低压压铸工艺获得来自北美轮制造的工件。一个工件与热电偶仪器不形成，但行预加热循环（协议第3节，步骤3.3-3.5）来捕获方法的这一方面中的温度在整个坯件的表面上的分布。这个响应示于<strong>图5。</strong>另外3个样品变形各级，其中包括获得两项形成通行证高水平的变形之一。前两个样本，对后者的样品进行第一遍有助于理顺与壁厚不大明显改变工件。后者样品峰的壁厚减少为约10％，其中大部分是在第二巴实现SS。截面和的铸态坯件和微观多遍样品中获得的那些示于<strong>图6。</strong>这里，示出了铸态组织到显著通过用树突特征勉强可辨别的方法来改进。枝晶间共晶是由所施加的变形打破，建立一个更均匀的微观组织比在铸态。这改善了整个延展性以及组件的疲劳和断裂性能。作者已经先前所述工件的几何形状，在壁厚特定横截面的变化，观察到的缺陷和尺寸变化的更多细节在微观结构上的全套样品<sup class="xref"><sup><sup class="xref">8,13</sup></sup></sup>的。 </p><p class="jove_content" fo:keep-together.within-page="1"><img alt="图5" src="/files/ftp_upload/55061/55061fig5.jpg" /><br /> <strong>图5:</strong> <strong>芯棒和b的典型的温度分布</strong><html>平直。与加热系统获得的空白，芯棒的一位代表瞬态热响应。垂直虚线指示，其中夹具预热步骤期间收紧，黑色箭头表示成形。最后垂直线示出了加热系统被关闭，而系统冷却。 </p><p class="jove_content" fo:keep-together.within-page="1"><img alt="图6" src="/files/ftp_upload/55061/55061fig6.jpg" /><br /> <strong>图6:铸态形成的结果。</strong>在作为接收的，铸态具有330毫米（顶部）的最小内径空白表面和几何两遍被变形以提供所示的结果（中间）。铸态枝晶组织（左下）明显被成形操作和随后的T6热处理（右下），为与光学显微镜<sup class="xref"><sup><sup class="xref">8,13</sup></sup></sup>观察修改。ig6large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 </p>

Watch this Scientific Journal Video about Experimental Procedure for Warm Spinning of Cast Aluminum Components at JoVE.com

Experimental Procedure for Warm Spinning of Cast Aluminum Components

<p class="jove_content">对于仪表温暖回转成型采用定制的工业缩放设备铸铝合金的实验方案提出。实验的考虑包括热和机械作用进行了讨论，以及与汽车车轮的全面处理相似。 </p>

铸铝零部件的暖纺纱实验程序

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to ...

experimental-procedure-for-warm-spinning-of-cast-aluminum-components

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Unit 1

Rotation and Rigid Bodies

SCIENTISTS IN ACTION

9.4K 次观看.  University of Manchester. 对于仪表温暖回转成型采用定制的工业缩放设备铸铝合金的实验方案提出。实验的考虑包括热和机械作用进行了讨论，以及与汽车车轮的全面处理相似。 

视频: Experimental Procedure for Warm Spinning of Cast Aluminum Components

Enthalpy of Reaction

Enthalpy of Reaction and Measurement of Heat by Calorimeter - procedure

反应焓

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

	Collecting Data for Calculating the Heat Capacity of a CalorimeterExpand
	This experiment will ...

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Metal Flame Emission

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Metal Flame Emission Testing<button class="expand">Expand</button>
	<p>In this lab, you will excite the electrons of six metal chloride salts with heat from a flame and measure the wavelength of light emitted by the relaxing electrons. The emitted light is in the visible spectrum, so you will see different colored flames for the different metals.</p>
	<p>At the end of the lab, you will measure the emission spectrum of a sparkler and use the data you collected from the metal salts to identify the metals in the sparkler. To help with this process, make a table in your lab notebook to record the wavelengths emitted from ambient light, the salts, and the sparkler.</p>
	<h4><strong>Table 1: Observed Wavelengths</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>Run #</strong></td>
				<td style="text-align: center;"><strong>Source</strong></td>
				<td style="text-align: center;"><strong>Recorded wavelength(s)</strong></td>
			</tr>
			<tr>
				<td style="text-align: center;">1</td>
				<td style="text-align: center;">Room lights</td>
				<td></td>
			</tr>
			<tr>
				<td style="text-align: center;">2</td>
				<td style="text-align: center;">NaCl</td>
				<td></td>
			</tr>
			<tr>
				<td style="text-align: center;">3</td>
				<td style="text-align: center;">LiCl</td>
				<td></td>
			</tr>
			<tr>
				<td style="text-align: center;">4</td>
				<td style="text-align: center;">KCl</td>
				<td></td>
			</tr>
			<tr>
				<td style="text-align: center;">5</td>
				<td style="text-align: center;">SrCl<sub>2</sub></td>
				<td></td>
			</tr>
			<tr>
				<td style="text-align: center;">6</td>
				<td style="text-align: center;">BaCl<sub>2</sub></td>
				<td></td>
			</tr>
			<tr>
				<td style="text-align: center;">7</td>
				<td style="text-align: center;">CuCl<sub>2</sub></td>
				<td></td>
			</tr>
			<tr>
				<td style="text-align: center;">8</td>
				<td style="text-align: center;">Sparkler</td>
				<td></td>
			</tr>
		</tbody>
	</table>
	<p><a href="https://www.jove.com/CDNSource/lm/labs/48/Table_1._Observed_Wavelengths.xlsx" target="_blank">Click Here to download Table 1</a></p>
	<p>During this lab, you will hold a salt-coated applicator at the edge of a Bunsen burner flame to excite the metal salts. If the applicator catches fire, immediately quench it in a beaker of water. For excitation, you will hold a detector near the flame and the sparkler to measure the wavelengths of the emitted light. Keep a safe distance to protect yourself and the detector. As some tasks are performed simultaneously, we suggest that you work in groups of four with each student completing tasks as needed.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-4">
		<div class="lab-step">Put on a lab coat, safety glasses, and nitrile gloves.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Set up the Bunsen burner in the fume hood.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Fill a 400-mL beaker with tap water and bring it to the hood. Place the salts, applicators, and tap water within easy reach on one side of the Bunsen burner.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Turn on the hand-held spectrophotometer and familiarize yourself with its components.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Create a new experiment and configure the spectrometer to measure emission intensity. Set the sample time to 200 ms and the number of readings at a given wavelength to 1. Record the settings and the experiment name in your lab notebooks.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Measure the spectrum of the room lights. Have one or two students hold the optical detector as close to the lights as possible without disconnecting the cables. Once ready, have a different student start the spectrometer. The spectrum should be clear, with minimal noise and no off-scale peaks. <strong>Note: </strong>If you have trouble, hold the probe in a nearly closed drawer or box to shield it from sunlight while pointing it at the room lights.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Immediately capture the spectrum when it looks good. Confirm that you have a high-quality spectrum before saving it. Record the wavelengths of the peaks in your data table.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Measure the emission spectra of the metal salts. Ignite the Bunsen burner and adjust the collar until the flame distinctly separates into an inner and outer flame.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Bring the spectrometer to the hood and arrange the cables so that the detector can be held about one inch from the flame.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Have one student prepare the spectrometer for the run. This student should have a clear view of the burner so they can begin acquiring data as soon as the salt enters the flame. Then, have another student hold the detector no closer than one inch from the flame. <strong>Note: </strong>Any closer risks damaging the detector. But you won&#39;t get a clear spectrum if the detector is too far away.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Have a different student take one of the applicators from the beaker of water and dip it into the tube of NaCl to coat the wet cotton with the salt. Then, carefully insert the salt-coated applicator about 1 mm into the outer flame, which will change color.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Start the spectrometer when the applicator enters the flame.<strong> Note: </strong>If the peak intensities are off-scale, adjust the detector position until all peaks are within detection limits. If the flame color change is hard to see, pick up more salt on the same applicator and try again until you see an intense color. If the spectrum is noisy or weak, try pointing the detector at a different part of the flame.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">When you see a good spectrum, capture and save it. Everyone should review the spectrum to ensure that it is of good quality. Write down the emission wavelengths in your table.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Submerge the NaCl applicator in your wastewater beaker. Always use a different applicator for each salt.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Follow the same procedure to test the remaining five salts, being careful to avoid cross-contamination between the salts. Once you have tested the last salt and recorded the wavelengths, set up data collection for the sparkler.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">At the instructor&#39;s hood, light the sparkler with the Bunsen burner and place it handle down in the Erlenmeyer flask. Remember, the sparks may be very hot. Turn off the gas to extinguish the Bunsen burner.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">As one student holds the detector close to the sparkler, have another student start data collection. Position the detector to get as many peaks in scale as possible without losing the less intense peaks.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Capture and save the spectrum once it looks good. Remember to write down the wavelengths in your table. <strong>Note: </strong>If the sparkler is long-lived, collect a second spectrum and either choose the best one or keep them both for the analysis.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">Let the sparkler burn out in the hood while you send the collected data to everyone in the group and shut down the data acquisition system.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Bring the copper, barium, and strontium tubes to the waste hood and thoroughly rinse the tubes with deionized water into the designated waste container.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Flush the sodium, potassium, and lithium salts down the drain and rinse the remaining test tubes. Put away the test tubes and the other equipment.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Once the ashes and sparkler handle have cooled, dump them in the trash.</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">First, plot the data for each run with intensity on the y-axis and wavelength on the x-axis.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Compare the sparkler spectrum to the background spectrum from the room lights. Identify which small peaks may be from the room lights.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Compare the metal spectra to the sparkler spectrum. Sodium appears to be the source of the peak at about 589 nm. There are no peaks matching the lithium spectrum, but potassium matches the large peak at 770 nm.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">The sparkler spectrum doesn&#39;t seem to have strontium peaks. However, barium is a good match for several peaks in the sparkler spectrum. Lastly, no copper seems to be present in the sparkler. Thus, we conclude that the sparkler was burning sodium, potassium, and barium when the spectrum was acquired.</div>
		</li>
	</ul>
	</li>
</ol>

金属火焰发射

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

	Metal Flame Emission TestingExpand
	In this lab, you will excite the electrons of six metal ...

Balmer Series

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Spectral Emission Lines of Hydrogen, Helium, and Neon<button class="expand">Expand</button>
	<p>In this experiment, you will use a spectrophotometer to measure the distinct wavelengths of light emitted in the UV and visible range by electron relaxation in hydrogen, helium, and neon. Before starting the lab, make a table in your lab notebook for the elements that you will analyze, the color of the light that you observe from the lamps, and the recorded wavelengths.</p>
	<h4><strong>Table 1: Emission Wavelengths</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>Elements</strong></td>
				<td style="text-align: center;"><strong>Color</strong></td>
				<td style="text-align: center;"><strong>Distinct wavelengths, &#955; (nm)</strong></td>
			</tr>
			<tr>
				<td style="text-align: center;">H</td>
				<td style="text-align: center;"></td>
				<td style="text-align: center;"></td>
			</tr>
			<tr>
				<td style="text-align: center;">He</td>
				<td style="text-align: center;"></td>
				<td style="text-align: center;"></td>
			</tr>
			<tr>
				<td style="text-align: center;">Ne</td>
				<td style="text-align: center;"></td>
				<td style="text-align: center;"></td>
			</tr>
		</tbody>
	</table>
	<p><a href="https://www.jove.com/CDNSource/lm/labs/54/Table_1._Emission_wavelengths.xlsx" target="_blank">Click Here to download Table 1</a></p>
	<ul class="lab-items">
		<li data-sub-note-item="1-2">
		<div class="lab-step">First, put on a lab coat, safety glasses, and nitrile gloves. We suggest students work in pairs for this experiment.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Turn on a hand-held spectrophotometer and create a new file for the hydrogen emission spectrum. Configure the spectrophotometer to measure emission intensity with a sampling time of 200 ms, with no sample averaging.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">When the instructor calls you, bring the spectrophotometer to the hydrogen lamp. The student holding the sensor should move close to the lamp, and the other should be ready to start the spectrophotometer acquisition.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">When the instructor turns on the lamp, hold the sensor at the center of the lamp and start displaying the spectrum. <strong>Note: </strong>Capture the spectrum as soon as it is clear and has minimal noise, as the lamp cannot be left on for more than 30 s at a time.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Save the hydrogen spectrum. Set up another experiment using the same parameters and acquire the spectrum for helium. Acquire a spectrum of neon in the same way.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Export your saved data, turn off the spectrophotometer, and put it away.</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">Set up the Rydberg formula to calculate the wavelengths of the Balmer series. <strong>Note:</strong> n<sub>initial</sub> is the number of the energy level where the excited electron starts, and n<sub>final</sub> is the energy level to which the electron relaxes. Set n<sub>final</sub> to 2.
		<h4><strong>Table 2: Frequency and Energy for Each Wavelength</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td><strong>Rydberg constant (m<sup>-1</sup>) </strong></td>
					<td style="text-align: center;">1.098 &#215; 10<sup>7</sup></td>
				</tr>
				<tr>
					<td><strong>c (m/s)</strong></td>
					<td style="text-align: center;">2.998 &#215; 10<sup>8</sup></td>
				</tr>
				<tr>
					<td><strong>h (J&#183;s)</strong></td>
					<td style="text-align: center;">6.626 &#215; 10<sup>-34</sup></td>
				</tr>
				<tr>
					<td style="text-align: center;"><strong>ni &#8594; nf</strong></td>
					<td style="text-align: center;"><strong>&#955;<sub>calculated </sub>(nm) </strong></td>
					<td style="text-align: center;"><strong>&#955;<sub>measured</sub> (nm) </strong></td>
					<td style="text-align: center;"><strong>v (THz) </strong></td>
					<td style="text-align: center;"><strong>E (eV) </strong></td>
				</tr>
				<tr>
					<td style="text-align: center;">7 &#8594; 2</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">6 &#8594; 2</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">5 &#8594; 2</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">4 &#8594; 2</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">3 &#8594; 2</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/54/Table_2._Frequency_and_energy_for_each_wavelength.xlsx" target="_blank">Click Here to download Table 2</a></div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Find the wavelength of light emitted by an electron relaxing from level 3 to level 2. Fill in the Rydberg constant for R<sub>H</sub> and solve for 1/&#955;. <strong>Note:</strong> The reciprocal of this value is the wavelength, which can be converted to nm.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Calculate the transitions from energy levels 4, 5, 6, and 7 in the same way. <strong>Note: </strong>You should see a good match between your data and your calculations.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">For each wavelength, calculate the frequency in THz and the energy in eV using the following equations, where c is the speed of light and h is Planck&#39;s constant.
		<ul>
			<li><img src="https://www.jove.com/CDNSource/lm/labs/54/54_Procedure_1.jpg" /></li>
			<li><img src="https://www.jove.com/CDNSource/lm/labs/54/54_Procedure_2.jpg" /></li>
		</ul>
		</div>
		</li>
	</ul>
	<p>Look at the calculated energies. You should see a trend of the energy gap increasing by less with each added energy level. This is reflected in the spacing of the peaks in the hydrogen emission spectrum. Helium and neon share this energy level spacing trend.</p>
	<p>From the helium spectrum, adding even one more electron makes the spectral series harder to calculate and identify. This is even more apparent in neon, which has eight more electrons than helium.</p>
	</li>
</ol>

The Hydrogen Atom: Bohr Model and Balmer Series - Procedure

Balmer 系列

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

	Spectral Emission Lines of Hydrogen, Helium, and NeonExpand
	In this experiment, you will use a ...

Temperature Dependence

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Temperature Dependent Decomposition of Hydrogen Peroxide<button class="expand">Expand</button>
	<p><em>We suggest that students work in pairs for this experiment. Equipment controls may vary.</em></p>
	<p>In this lab, you&#39;ll perform a decomposition reaction where a single compound breaks down into two or more simpler products. You will observe the decomposition of hydrogen peroxide into water and oxygen. This decomposition happens very slowly, so you will use iron (III) nitrate as a catalyst to lower the activation energy.</p>
	<p>During this process, iron undergoes a redox reaction and then returns to its starting oxidation state. You will be able to see this as a color change in your solution during the reaction. You&#39;ll perform the same reaction at four different temperatures and track the rate of the reaction by recording the pressure inside the flask. This way you can measure how quickly oxygen was produced in each experiment. You&#39;ll use this to calculate the reaction&#39;s activation energy.</p>
	<p><strong>Table 1. Estimate the apparent activation energy for the decompostion of hydrogen peroxide</strong></p>
	<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
		<tbody>
			<tr>
				<td><strong>Trial&#160;</strong></td>
				<td><strong>Temperature (&#8451;)</strong></td>
				<td><strong>&#916;P (kPa/s)</strong></td>
				<td><strong>1/T&#160;</strong></td>
				<td><strong>ln (&#916;P)</strong></td>
			</tr>
			<tr>
				<td>1</td>
				<td></td>
				<td></td>
				<td></td>
				<td></td>
			</tr>
			<tr>
				<td>2</td>
				<td></td>
				<td></td>
				<td></td>
				<td></td>
			</tr>
			<tr>
				<td>3</td>
				<td></td>
				<td></td>
				<td></td>
				<td></td>
			</tr>
			<tr>
				<td>4</td>
				<td></td>
				<td></td>
				<td></td>
				<td></td>
			</tr>
		</tbody>
	</table>
	<p><a href="/CDNSource/labs/51/Table_1._Estimate_the_apparent_activation_energy_of.xlsx" target="_blank">Click Here to download Table 1</a> &#160;</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-1">
		<div class="lab-step">Before starting this experiment, put on a lab coat, safety glasses, and nitrile gloves.</div>
		</li>
		<li data-sub-note-item="1-2">
		<div class="lab-step">Ensure that your hot plate is off and then place a 600-mL beaker on the hot plate.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Connect vacuum tubing to the barbed sidearm of a 125-mL B&#252;chner filter flask, and carefully clamp the filter flask in the 600-mL beaker so that the sidearm is just above the top of the beaker.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Fill a 400-mL beaker with deionized water., and pour the water into the 600-mL beaker until the water level is about 2&#8211;3 cm below the side arm.<br />
		<strong>NOTE</strong>: Make sure that the water is not able to get into the flask or vacuum line.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Immerse the thermometer in the water, clamping it in place so that the end is in contact with the outer wall of the flask. Ensure that you can read the current temperature, as well as the 40, 60, and 80 &#176;C marks.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Make sure that each hole of the 2-hole adapter is fitted with a tapered locking adapter. Check that all the adapters are firmly seated, since any air that escapes around them will affect your data.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Lock a 2-way stopcock into one of the stopper adapters. Then, lock one end of the flexible tubing into the second adapter with the other end into the connector of the gas pressure sensor.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Turn on the data acquisition device for the gas pressure sensor and ensure that the pressure is displayed in kPa.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Set the acquisition rate to two samples per second and the duration to 300 s. Then, display the pressure in real-time.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Label a 400-mL beaker as &#8216;waste&#8217;, a 50-mL beaker as &#8216;0.5 M Fe(NO<sub>3</sub>)<sub>3</sub>&#8217;, and a 100-mL beaker as &#8216;3% w/w hydrogen peroxide&#8217;.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Place a few paper towels on the work surface as a clean area for glassware that you will reuse. Keep a supply of paper towels on hand for later.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Then, bring the 50-mL and 100-mL beakers to the stock solution area. Pour about 30 mL of 0.5 M Fe(NO<sub>3</sub>)<sub>3</sub> in the 50-mL beaker and 100 mL of 3% w/w hydrogen peroxide in the 100-mL beaker.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Back at your workspace, setup a 20-mL volumetric pipette and fill it to the mark with 3% w/w hydrogen peroxide. Dispense the hydrogen peroxide into the filter flask and set the volumetric pipette aside.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Adjust the thermometer as needed so that it contacts the flask below the hydrogen peroxide solution level.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Fit the rubber stopper into the mouth of the filter flask, being careful not to loosen the connections to the sensor and the 2-way stopcock.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Check that the 2-way stop is closed. Open the vacuum line and monitor the pressure as it decreases. This will seal the stopper in the flask. Once the pressure reaches 10 kPa, close the vacuum.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Monitor the pressure for at least 1 min to confirm there are no slow leaks.<br />
		<strong>NOTE</strong>: If the pressure immediately starts rapidly increasing, there is a leak in your setup, so tighten the connections and try again until the pressure holds at 10 kPa when the vacuum line is closed.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Draw 5 mL of 0.5 M Fe(NO<sub>3</sub>)<sub>3</sub> into a 20-mL syringe. Expel all air from the syringe so that it only contains the solution.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Lock the syringe into the top of the 2-way stopcock. You are now ready to start the room temperature trial, so record the water temperature in your lab notebook.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Start acquiring gas pressure data. Allow the device to record data for about 15 s, then open the stopcock and quickly close it once all of the Fe(NO<sub>3</sub>)<sub>3</sub> has entered the flask. The observed increase in pressure is from the evolution of oxygen gas produced by the decomposition of hydrogen peroxide.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">Once the data collection finishes, save your data. Then, disconnect the syringe and open the stopcock to vent the flask.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Take out the rubber stopper, carefully remove the thermometer from the clamp and the flask from the beaker, and disconnect the vacuum tubing from the filter flask.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Empty the flask into the waste beaker. Try not to get liquid in the side arm. Dry the outside of the flask with paper towels.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Rinse the interior of the flask with deionized water and pour the rinse into the waste beaker. If any liquid gets into the side arm, remove it with paper towels.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Reconnect the flask to the vacuum line and clamp it in the 600-mL beaker in contact with the thermometer.</div>
		</li>
		<li data-sub-note-item="1-27">
		<div class="lab-step">Turn on the hotplate and heat the water around the flask until the thermometer reads 80 &#176;C. Then, turn off the heat.</div>
		</li>
		<li data-sub-note-item="1-28">
		<div class="lab-step">Then, add 20 mL of 3% w/w hydrogen peroxide to the flask.</div>
		</li>
		<li data-sub-note-item="1-29">
		<div class="lab-step">Dry the stopper with paper towels. Do this after each trial to ensure that the stopper has a snug fit in the neck of the beaker and fit the stopper in the flask.</div>
		</li>
		<li data-sub-note-item="1-30">
		<div class="lab-step">Check that the stopcock is closed and evacuate the flask to about 10 kPa. Then, close the vacuum and confirm that there are no leaks.</div>
		</li>
		<li data-sub-note-item="1-31">
		<div class="lab-step">Draw 5 mL Fe(NO<sub>3</sub>)<sub>3</sub> solution into the syringe, expel the air from the syringe, and connect it to the stopcock.</div>
		</li>
		<li data-sub-note-item="1-32">
		<div class="lab-step">Record the temperature shown on the thermometer in your lab notebook, then, start collecting data.</div>
		</li>
		<li data-sub-note-item="1-33">
		<div class="lab-step">Wait about 15 s and introduce the Fe(NO<sub>3</sub>)<sub>3</sub> solution in the same way as before.<br />
		<strong>NOTE:</strong> As the pressure approaches 150 kPa, the stopper may pop off!</div>
		</li>
		<li data-sub-note-item="1-34">
		<div class="lab-step">After data collection finishes, save the data, vent and clean the filter flask, and set up for the third trial.</div>
		</li>
		<li data-sub-note-item="1-35">
		<div class="lab-step">Fill the 400-mL beaker with ice and add some to cool the water to about 60 &#176;C.</div>
		</li>
		<li data-sub-note-item="1-36">
		<div class="lab-step">Perform the third trial in the same way as before. Remember to dry the stopper and the inside of the flask and to record the temperature prior to data collection.</div>
		</li>
		<li data-sub-note-item="1-37">
		<div class="lab-step">After the data is collected for that trial, cool the water to about 40 &#176;C and perform the fourth trial.</div>
		</li>
		<li data-sub-note-item="1-38">
		<div class="lab-step">Once you have finished all four trials, empty the filter flask and rinse it into the waste beaker one last time.</div>
		</li>
		<li data-sub-note-item="1-39">
		<div class="lab-step">Dispose of any excess 0.5 M Fe(NO<sub>3</sub>)<sub>3</sub> and the contents of the waste beaker in a container labeled for aqueous iron waste.</div>
		</li>
		<li data-sub-note-item="1-40">
		<div class="lab-step">Then, disassemble the apparatus and pour the leftover ice, water, and hydrogen peroxide in the sink. Wash your glassware following your lab&#39;s standard protocol.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="1" data-parent-collapse="">Results<button class="expand">Expand</button>
	<p>The decomposition of hydrogen peroxide with iron is a complex, multi-step process that we can&#39;t easily describe in a single equation. However, we can estimate the apparent activation energy from the rate of oxygen production and compare it to the apparent activation energy of the un-catalyzed process.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-1">
		<div class="lab-step">Find the rate of pressure change, which is directly proportional to the rate of oxygen production. For each experiment, make a plot of pressure with respect to time and find the point where the reaction started.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Identify the maximum pressure attained and determine the slope between the two points.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Once you&#39;ve determined the slopes and the corresponding temperatures in Kelvin for all of the temperatures, use the Arrhenius equation to estimate the apparent activation energy of this reaction.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Take the reciprocal of the temperatures in Kelvin and the natural log of the rate of change in pressure. Remember that the rate constant k is essentially equal to the change in pressure.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Make an Arrhenius plot and find the slope of the line.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">The slope is equal to the negative activation energy over the universal gas constant, so multiply the slope by the negative universal gas constant to get the apparent activation energy of the iron catalyzed decomposition reaction. You&#39;ll see a value in the range of 35&#8211;60 kJ/mol because the iron catalyst made the decomposition take less energy. The apparent activation energy of the uncatalyzed decomposition of hydrogen peroxide is around 78 &#8211; 88 kJ/mol.</div>
		</li>
	</ul>
	</li>
</ol>

Temperature Dependence and Arrhenius Equation - Procedure

温度依赖性

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

	Temperature Dependent Decomposition of Hydrogen PeroxideExpand
	We suggest that students work ...

Electrolytic Cells

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Electrolytic Cells<button class="expand">Expand</button>
	<p>In this experiment, you will be assembling an electrolytic cell to perform electroplating. An electrolytic cell contains an anode and cathode connected by a power source, which drives the nonspontaneous redox reaction in the cell. When the anode material is oxidized, the ions travel to the cathode, where they are reduced and plated.</p>
	<p>In the case of this experiment, the electrolytic cell contains a copper anode and a brass key for the cathode. Oxidation of the anode creates copper(2+) ions, which are then reduced on the brass key, forming a thin plating of solid copper.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-3">
		<div class="lab-step">Put on gloves, safety goggles, and a lab apron, which must be worn at all times.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Obtain one 10-ohm resistor, one copper sheet electrode, one copper wire, and one piece of emery paper.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Use the emery paper to polish the brass key and the copper sheet. Rinse the key and the copper electrode with water. The brass key will be the cathode, and the copper sheet will be the anode.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Take one 50-mL beaker and a watch glass to the instructor&#39;s hood and obtain approximately 20 mL of acetone. Place the watch glass on top of the beaker to prevent evaporation and bring it back to your bench.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Label the other 50-mL beaker as &#39;organic waste&#39;.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Use a disposable pipette to rinse the copper electrode and key with acetone. Collect excess in the waste beaker. Place the key and copper electrode on a paper towel to dry.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Measure the initial masses of the key and copper electrode and record their values in your lab notebook.
		<h4><strong>Table 1: Moles of Cu Transferred</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td></td>
					<td style="text-align: center;"><strong>Mass of key (g) </strong></td>
					<td style="text-align: center;"><strong>Change in mass (g) </strong></td>
					<td style="text-align: center;"><strong>Moles Cu plated </strong></td>
					<td style="text-align: center;"><strong>Mass of Cu electrode (g) </strong></td>
					<td style="text-align: center;"><strong>Change in mass (g) </strong></td>
					<td style="text-align: center;"><strong>Moles Cu lost </strong></td>
				</tr>
				<tr>
					<td style="text-align: center;">0 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">5 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">1<sup>st</sup> 30 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">2<sup>nd</sup> 30 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/53/Table_1._Moles_of_Cu_Transferred.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Set up the electrolytic cell. Use one electrical wire with alligator clips to connect the negative terminal on the battery to the current probe. Wrap the 10-ohm resistor around the other end of the current probe.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Use another wire to connect the positive terminal on the battery to the copper electrode.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Wrap the copper wire around the brass key and use an electrical wire to connect the resistor on the current probe to the copper wire on the brass key.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Obtain about 200 mL of concentrated copper sulfate in a 250-mL beaker. The amount does not need to be exact. Bring the beaker back to your bench and set it on the stir plate. Carefully, place a magnetic stir bar in the beaker and turn the stir setting on to high.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Connect the data acquisition system to the current probe and allow the data acquisition system to sense the probe. It should return a reading in amps. Change the rate to two scans per min and the duration to 5 min.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Place the brass key in the beaker. Hang it off the side of the beaker so that the key is almost completely submerged but does not touch the magnetic stir bar. <strong>Note: </strong>The copper wire should not be in the solution.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Place the copper electrode in the beaker, bending it so that it hangs over the edge of the beaker. Ensure that it is not touching the stir bar or the brass key.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Start the scan and let it collect data for 5 min. This will act as a test run to make sure plating occurs on the brass key.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">After the scan ends, remove the key and copper electrode. The copper plating on the brass key should be evident. If it is not visible, check your circuit to make sure that the battery is connected in the correct orientation.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Once you have completed a successful 5-min plating, disconnect the key and copper electrode from the wiring. Remove the copper wire from the key and rinse the key and copper electrode with water and then acetone. Lay them on a paper towel to dry.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Measure the masses of the key and the copper electrode and record them in your lab notebook.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Reconnect the key and copper electrode and place them back in the solution like before. Restart the run on the data acquisition system, making sure that the rate is set to two scans per min. With the duration set to 30 min, allow the electroplating process to run.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">After the scan is complete, remove the electrode and key from the solution, disconnect them from the wires, and rinse them with water and then acetone. Allow them to dry on a paper towel, then weigh them and record their masses in your notebook.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Reassemble the setup and repeat the electroplating for a second 30-min trial. When the scan is complete, remove the key and copper electrode, rinse them like before, and record their mass.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Save the recorded data as a text file on a flash drive.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">To clean up, turn the stir setting off and remove the stir bar from the solution using forceps. Dispose of the acetone in the organic waste container provided by your instructor. The copper sulfate solution can be reused for future labs, so pour the concentrated copper sulfate back into the carboy.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Rinse all of your glassware with water and return it to the instructor.</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">First, calculate the total charge Q that flowed through the system during the different trials. One coulomb is the quantity of electricity flowing through a wire carrying 1 ampere of current in 1 s, thus Q = I x t.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Review the current probe data for the first 5-min electroplating trial.<strong> Note: </strong>If the current dropped to 0 or close to 0 at the end of the trial, then the electrons stopped flowing from the copper electrode to the key. Only use the values recorded before the drop in current occurred. If the current drop to 0 early in the plating process, repeat the trial.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">The current varies over time, so calculate the average current, I.
		<h4><strong>Table 2: Moles of Electrons Transferred</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>Trial</strong></td>
					<td style="text-align: center;"><strong>Time (s) </strong></td>
					<td style="text-align: center;"><strong>Current<sub>average</sub> (A) </strong></td>
					<td style="text-align: center;"><strong>Total charge (C) </strong></td>
					<td style="text-align: center;"><strong>Moles (e?) </strong></td>
				</tr>
				<tr>
					<td style="text-align: center;">5 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">1<sup>st</sup> 30 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">2<sup>nd</sup> 30 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">Total</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/53/Table_2._Moles_of_Electrons_Transferred.xlsx" target="_blank">Click Here to download Table 2</a></div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Use the average current over the total time to determine the total charge transferred during electroplating, Q. About 20 coulombs were transferred during the 5-min trial, and between 110 and 120 coulombs were transferred during each 30-min trial. The total charge transferred over the entire 65-min electroplating process was about 250 coulombs.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Use the total charge transferred to calculate the moles of electrons plated during each trial. The moles of electrons plated equals the total charge transferred divided by the Faraday constant. The Faraday constant represents the magnitude of electric charge per mole of electrons and is determined by multiplying the charge of an electron by Avogadro&#39;s constant.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Determine the moles of electrons that were transferred for the 5-min and 30-min trials.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Calculate the moles of copper that were plated on the key after each trial. Similarly, determine the moles of copper lost from the copper sheet electrode.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Compare the moles of copper that were lost from the electrode to the amount that was plated to the brass key. The numbers should be close.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Check to see if these values match what is expected based on the number of moles of electrons that were transferred. The reduction of 1 mole of copper(2+) ions requires 2 moles of electrons to produce 1 mole of solid copper.</div>
		</li>
	</ul>
	</li>
</ol>

Electrolytic Cells: Construction and Electroplating - Procedure

电解槽

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

	Electrolytic CellsExpand
	In this experiment, you will be assembling an electrolytic cell to ...

Basic Organic Chemistry Techniques

<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="">Synthesis of Benzoic Acid<button class="expand">Expand</button>
	<p>In this lab, you&#39;ll learn several important techniques that you&#39;ll use throughout this class. This includes measuring the mass or volume of reactants and products, methods of heating and cooling reaction mixtures, proper selection and handling of glassware, and separating solids and liquids by vacuum filtration. First, you&#39;ll synthesize benzoic acid by protonating sodium benzoate with hydrochloric acid, or HCl, using water as the solvent. Sodium benzoate is very soluble in water, but benzoic acid is not, so you can filter the solid product out of the solution.</p>
	<p>You&#39;ll use vacuum filtration, which is used for powdery solids, to filter out the benzoic acid. Benzoic acid is less soluble in water at lower temperatures, so you&#39;ll collect more product if you cool the reaction solution before you filter it. When you do this lab, remember that HCl is toxic and a strong acid. It&#39;s always best to work with strong acids and organic solvents in a fume hood. If you spill any HCl, follow your lab&#39;s procedures for neutralizing and cleaning up strong acids.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-3">
		<div class="lab-step">Put on a lab coat, safety glasses, and nitrile gloves. Change your gloves if you get acid or organic solvent on them.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Bring a clean 50-mL beaker and your lab notebook to the balance, and then tare a clean empty weighing boat on the balance.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Use a clean spatula to measure out ~2 g of sodium benzoate.<strong> Note:</strong> Stay between 1.9 and 2.1 g.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Dispose of any extra sodium benzoate into the appropriate waste container. Close the bottle of sodium benzoate when you&#39;re done with it.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Write down the mass of sodium benzoate and pour it into your beaker. Clean the spatula with a lab wipe so that it can be used again and return to your fume hood.
		<h4><strong>Table 1: Reaction yield of benzoic acid</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>Mass of sodium<br />
					benzoate (g)</strong></td>
					<td style="text-align: center;"><strong>Moles of sodium<br />
					benzoate</strong></td>
					<td style="text-align: center;"><strong>Volume of<br />
					HCl (mL)</strong></td>
					<td style="text-align: center;"><strong>Moles of<br />
					HCl</strong></td>
					<td style="text-align: center;"><strong>Moles of benzoic<br />
					acid</strong></td>
					<td style="text-align: center;"><strong>Mass of benzoic<br />
					acid (g)</strong></td>
				</tr>
				<tr>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td><strong>Theoretical yield</strong></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">-</td>
					<td style="text-align: center;">-</td>
					<td style="text-align: center;">-</td>
					<td style="text-align: center;">-</td>
					<td><strong>Percent yield</strong></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/56/Table_1._Reaction_yield_of_benzoic_acid.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Get a clean 10-mL graduated cylinder and measure 10 mL of deionized water. Pour the water into the beaker of sodium benzoate. Stir the solution with a glass rod until the sodium benzoate has completely dissolved.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Obtain a clean 5-mL graduated cylinder and measure 5 mL of 3 M HCl. <strong>Note: </strong>If you pour too much, use a Pasteur pipette to transfer the excess to a small beaker labeled &#8216;acid waste&#8217;. Close the bottle and put it back when you&#39;re done.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Use a clean Pasteur pipette to draw up a small amount of HCl from your graduated cylinder. Start adding the HCl to the sodium benzoate solution at a rate of about one drop every 6 seconds or 10 drops/min. Stir the solution frequently with the glass rod. This should take about 10 min. <strong>Note:</strong> As you add more HCl, you&#39;ll start to see benzoic acid precipitating from the solution.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">When you are done, fill a 600-mL beaker about halfway with crushed ice and add tap water to just fill the spaces between the ice to make an ice bath.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Place the ice bath by a lab stand in your fume hood and use a medium clamp to hold the reaction beaker in the bath. Make sure that the surface of the solution is below the ice.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Clamp a thermometer in the reaction solution.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">While the reaction cools, obtain 25 mL of deionized water in a 50-mL graduated cylinder. Place the graduated cylinder in a 600-mL beaker and pack ice around it to cool the water.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Once the reaction solution reaches 10 &#176;C, it&#39;s ready to be filtered. Set up another lab stand and obtain a clean 250-mL filter flask. Clamp the flask upright on the lab stand.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Ensure that your vacuum tubing is connected to the vacuum source, and then carefully push the free end of the tubing onto the barbed arm of the flask.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Place a rubber adapter and a B&#252;chner funnel in the mouth of the flask. Confirm that the reaction solution has reached 10 &#176;C and remove the thermometer from the beaker.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Obtain a piece of circular filter paper and place it in the B&#252;chner funnel so that the small holes are completely covered.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Get a new Pasteur pipette, and use a few drops of cold deionized water to wet the filter paper. <strong>Note: </strong>This helps keep the filter paper in place when you pour the solution into the funnel.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Open the vacuum line part way to reduce the pressure in the flask.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Remove the beaker from the ice bath, stir the solution well with the glass rod until the solid is swirling around in the liquid, and then slowly pour it onto the filter paper. <strong>Note:</strong> If the liquid does not move quickly through the funnel, make sure that there are no gaps between the funnel, adapter, and flask, and then gradually open the vacuum until the liquid rapidly flows into the flask.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">Use a clean Pasteur pipette to rinse the inner walls of the beaker with ~10 mL of cold deionized water and pour the rinse into the funnel. Pour the rest of the cold deionized water over the benzoic acid on the filter to wash it. <strong>Note:</strong> This is an important step that removes impurities, side products, and unreacted compounds.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Leave the benzoic acid in the funnel with the vacuum running until it is completely dry. <strong>Note: </strong>This usually takes ~2 h, so let&#39;s continue to the second half of the lab in the meantime.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Refluxing Tetrahydrofuran (THF) and Measuring Product Mass<button class="expand">Expand</button>
	<p>While your benzoic acid dries, you&#39;ll practice refluxing tetrahydrofuran, or THF, which has a boiling point of 66 &#176;C. THF is volatile, flammable, and an irritant, so avoid letting it touch your skin and always work with it in a fume hood. Refluxing is a technique that constantly condenses the vapor and returns it to the flask. This allows reactions to be performed at high temperatures, such as at the solvent&#39;s boiling point, without losing the solvent to evaporation.</p>
	<p>Refluxing is achieved with a special piece of glassware called a condenser, which is attached directly to your flask. The condenser is cooled with water flowing through the outer chamber. As vapor rises through the condenser, it loses heat to the cool walls, condenses, and drips back into the flask.</p>
	<p>Refluxing is usually performed in a round-bottom flask. These flasks must be heated in a heating bath or with specialized equipment, but they provide more even heating than an Erlenmeyer flask or beaker as a result. Water baths are typically used for experiments performed below 80 &#8211; 100 &#176;C.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-4">
		<div class="lab-step">Set up the glassware and equipment for reflux. Place a lab jack by your available lab stand and set a stirring hotplate on top of it. Clamp a 50-mL round-bottom flask at least 12 cm above the hotplate.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Bring a 50-mL graduated cylinder to the solvent hood and measure 25 mL of THF. If you pour too much, label a small beaker &#8216;organic waste&#8217; and pipette the excess into that. Remember to cap the bottle when you&#39;re done.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Carefully pour the THF into the round-bottom flask, clean up any spills with a lab wipe or paper towel, and add a small oblong stir bar to the flask.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Position a medium clamp ~20 cm above the flask. Obtain a condenser and apply vacuum grease to the lower ground-glass joint.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Fit the condenser into the flask and rotate them in opposite directions until the vacuum grease is evenly spread between the two ground-glass surfaces.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Clamp the condenser in place and use a lab wipe to remove excess grease from the connection between the two pieces of glassware.</div>
		</li>
		<li data-sub-note-item="2-10">
		<div class="lab-step">Attach rubber tubing to each of the ports on the condenser. Place the free end of the tubing connected to the top port, which is the outlet, in the drain. Connect the free end of the tubing from the bottom port, which is the inlet, to the waterline.</div>
		</li>
		<li data-sub-note-item="2-11">
		<div class="lab-step">Fill a 250-mL beaker with ~200 mL of tap water and place this water bath on the hotplate. Use the lab jack to raise the bath until the water level is about 2/3 of the way up the spherical part of the flask. This will ensure the THF heats evenly.</div>
		</li>
		<li data-sub-note-item="2-12">
		<div class="lab-step">Secure a thermometer (range 0 &#8211; 100 &#176;C) in the bath using the thermometer clamp.</div>
		</li>
		<li data-sub-note-item="2-13">
		<div class="lab-step">Slowly open the water tap, watch the condenser for leaks as it fills, and confirm that the water is flowing into the drain.</div>
		</li>
		<li data-sub-note-item="2-14">
		<div class="lab-step">Slowly turn up the magnetic stirrer until the THF is stirring well. If the stir bar bounces around, turn down the stir motor and try again more slowly.</div>
		</li>
		<li data-sub-note-item="2-15">
		<div class="lab-step">Start heating the water bath to about 70 &#176;C until the THF starts to boil. <strong>Note: </strong>You&#39;ll see vapor condensing in the lower part of the condenser).</div>
		</li>
		<li data-sub-note-item="2-16">
		<div class="lab-step">Monitor the refluxing THF for 10 min. <strong>Note:</strong> Turn down the heat if the bath goes above 70 &#176;C or if vapor leaves the condenser.</div>
		</li>
		<li data-sub-note-item="2-17">
		<div class="lab-step">After 10 min, remove the thermometer and turn off the heat and the stir motor. Carefully lower the lab jack until the flask is clear of the water bath. Wait at least 10 more min for the setup to cool, then unplug and remove the hotplate.</div>
		</li>
		<li data-sub-note-item="2-18">
		<div class="lab-step">Turn off the water tap, unclamp the condenser, and carefully detach it from the flask. Tilt the condenser until most of the water has flowed through the outlet tubing into the drain. Then, disconnect the inlet tubing from the condenser and let the remaining water flow into the drain. Do the same for the outlet tubing.</div>
		</li>
		<li data-sub-note-item="2-19">
		<div class="lab-step">Use lab wipes to remove the vacuum grease from the condenser and the flask, then retrieve the stir bar from the flask.</div>
		</li>
		<li data-sub-note-item="2-20">
		<div class="lab-step">Bring the flask to the waste hood and empty it into the non-halogenated organic waste container. Pour any excess HCl or THF into the acid and organic wastes, respectively. Empty the ice and water baths into the sink and rinse the beakers with tap water.</div>
		</li>
		<li data-sub-note-item="2-21">
		<div class="lab-step">Clean most of your other glassware while the benzoic acid from earlier finishes drying according to your lab&#8217;s standard practices. Usually, you&#39;ll rinse your glassware both with an organic solvent, like acetone, and with detergent and deionized water. <strong>Note:</strong> Your lab may have specific procedures for glassware used with acids. If so, follow that procedure to clean the graduated cylinder used with HCl and your acid waste beaker, if applicable.</div>
		</li>
		<li data-sub-note-item="2-22">
		<div class="lab-step">Remove the reusable pipette bulbs and dispose of your pipettes in the glass waste container. Throw out used lab wipes and paper towels in the lab trash.</div>
		</li>
		<li data-sub-note-item="2-23">
		<div class="lab-step">Check on your benzoic acid. If it is dry, turn off the vacuum and break the vacuum seal by disconnecting the tubing from the filter flask. Gently place the funnel in it 250-mL beaker and bring it and your lab notebook to the balance.</div>
		</li>
		<li data-sub-note-item="2-24">
		<div class="lab-step">Tare a weighing boat and use a clean spatula to transfer the product to the weighing boat. Record the mass of your product in your lab notebook.</div>
		</li>
		<li data-sub-note-item="2-25">
		<div class="lab-step">Then, put the product in the lab trash and wipe off the spatula. Dispose of the filtrate in the aqueous waste container.</div>
		</li>
		<li data-sub-note-item="2-26">
		<div class="lab-step">Clean the rest of your glassware, throw out the filter paper and other waste in the lab trash, and put away your lab equipment. Lastly, clean the floor of your fume hood with a damp paper towel.</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 reaction yield for the protonation of sodium benzoate. Identify the reagent that the reaction runs out of first, which is called the limiting reagent.</div>
		</li>
		<li data-sub-note-item="3-2">
		<div class="lab-step">Calculate the number of moles of sodium benzoate and HCl that you used. <strong>Note:</strong> You used about 0.014 moles of sodium benzoate and 0.015 moles of HCl. Thus, the maximum yield of benzoic acid is equal to the starting amount of sodium benzoate in moles.</div>
		</li>
		<li data-sub-note-item="3-3">
		<div class="lab-step">Convert the mass of your benzoic acid to moles, divide that by the moles of sodium benzoate that you used, and multiply it by 100 to get the percent yield. <strong>Note:</strong> The recovered yield for this reaction is usually between 80% and 98% because a small amount of benzoic acid stays in solution. If the yield is above 100%, then it&#39;s likely that your product was still wet when you weighed it. Impurities, unreacted compounds, and products of side reactions can also affect the accuracy of yield calculations.</div>
		</li>
	</ul>
	</li>
</ol>

基本有机化学技术

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

	Synthesis of Benzoic AcidExpand
	In this lab, you&#39;ll ...

Melting Points

<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="">Determining the Melting Points of Naphthalene, Urea, and an Unknown Mixture<button class="expand">Expand</button>
	<p>In this experiment, you will measure the melting point range of two known substances, naphthalene and urea, by observing the melting phenomenon during heating. You&#39;ll then analyze a mixture of urea and an unknown substance to observe how the unknown impurity affects the melting point range.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-2">
		<div class="lab-step">Put on a lab coat, splash-proof safety glasses, and nitrile gloves.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Weigh ~1 mg of naphthalene using the analytical balance, and carefully, bring it back to your bench.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Transfer the naphthalene onto a watch glass, and then crush it using the metal spatula until it becomes a fine powder.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Carefully pick up one capillary tube and tap the open end on the powder to force some of the solid into the tube.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Obtain a long glass tube from the common bench and hold it upright over your bench. Pick up the capillary with the open end upward and then drop it through the glass tube. Allow the capillary to bounce off the benchtop to pack the solid at the bottom.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Retrieve the capillary and tap its open end on the naphthalene powder again to force more of it into the capillary. Continue loading naphthalene into the capillary and dropping it through the glass tube until 1 &#8211; 2 mL of powder is packed at the bottom of the capillary.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Use a rubber band to attach the capillary to a digital thermometer, with the bottom of the capillary just above the bottom of the thermometer. <strong>Note:</strong> Make sure that the rubber band is at least 8 &#8211; 9 cm above the solid in the capillary.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Set up a stirring hotplate and a lab stand in a fume hood and clamp the thermometer above the hotplate.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Place the provided mineral oil bath on the hotplate and add a magnetic stir bar. Start stirring the bath at a moderate speed over low heat.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Lower the thermometer and capillary setup into the oil bath until the sample is about 5 cm deep in the bath. <strong>Note:</strong> Make sure that the rubber band is above the mineral oil.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Increase the hotplate temperature to 60&#176;C, which is about 20&#176; below the melting point of naphthalene in the literature.<strong> Note:</strong> It will take about 10 min for the entire oil bath to reach the same temperature as the hotplate.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Once the bath reaches 60&#176;C, heat it to 75&#176;C at a rate of 5&#176;C/min. When the bath is close to the melting point of naphthalene (80&#176;C), heat the bath by 1 &#8211; 2 &#176;C/min while carefully observing the solid in the capillary.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">At the first drop of liquid in the capillary, record the temperature of the oil bath. Keep watching the capillary tube as you slowly increase the temperature. Record the temperature when the last piece of solid melts.
		<h4><strong>Table 1: Melting Points of Naphthalene, Urea, and an Unknown Mixture</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td></td>
					<td colspan="2" style="text-align: center;"><strong>Melting point temperature (&#176;C)</strong></td>
				</tr>
				<tr>
					<td><strong>Substance</strong></td>
					<td style="text-align: center;"><strong>Start</strong></td>
					<td style="text-align: center;"><strong>End</strong></td>
				</tr>
				<tr>
					<td>Napthalene</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Urea</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Urea + Unknown (trial 1)</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Urea + Unknown (trial 2)</td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/66/Table_1._Melting_points_of_naphthalene,_urea,_and_an_unknown_mixture.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Carefully remove the capillary and thermometer from the oil bath and set them aside to cool.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Weigh roughly 1 mg of urea and transfer it to a clean watch glass. Crush the urea to a powder. Load the powder into a capillary tube as before.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Attach the capillary to the thermometer with the rubber band. Heat the oil bath to 110&#176;C, which is about 20&#176; below the reported melting point of 132&#176;C for urea.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Insert the thermometer and capillary tube into the oil bath. Heat the bath to about 125&#176;C at 5&#176;C/min while watching the capillary.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">When the bath reaches 125&#176;C, heat the bath by 1 &#8211; 2&#176;C /min. Record the temperature when the first drop of liquid appears and when the last bit of solid melts.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Turn off the hotplate and remove the capillary and thermometer from the oil bath to allow them to cool.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Test the sample of urea mixed with an unknown impurity, which was prepared by your instructor. Perform two runs of this sample, so weigh 2 mg of the sample on the balance and transfer it to a watch glass.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">Crush the sample to powder and load two capillaries by tapping them on the powder and dropping them through the glass tube like before.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Once the oil bath has cooled to at least 80&#176;C, turn on the stir motor and set the hotplate to 80&#176;C. Attach one of the loaded capillaries to the thermometer and clamp them in the oil bath.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">In the first test run, increase the temperature by 10&#176;C/min until the sample has melted to determine the rough melting point range. Record the temperature when you see the first drop of liquid form and the last drop of liquid form to determine the rough melting point range.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Turn off the hotplate and allow it to cool. Once the oil bath has cooled to at least 80&#176;C, attach the second sample to the thermometer and clamp them in the bath. Turn the stir motor back on and set the hotplate to 80&#176;C.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">For the second test, heat the bath by 5&#176;C/min until you are close to the rough melting point range, and then continue heating by 1 &#8211; 2&#176;C/min to accurately capture the melting point range.</div>
		</li>
		<li data-sub-note-item="1-27">
		<div class="lab-step">When you have finished measuring the melting point of the urea mixed with the unknown substance, turn off the hotplate and detach the capillary tube from the thermometer. Dispose of your capillary tubes in the glass waste container.</div>
		</li>
		<li data-sub-note-item="1-28">
		<div class="lab-step">Return the mineral oil to your instructor, and clean all of your glassware using detergent and water.</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">First, look at the melting point range of naphthalene. These differences may be caused by experimental errors, such as heating the sample too quickly, or by impurities in the sample.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Next, check the results for the pure urea sample. Why is urea&#39;s melting point so much higher than naphthalene&#39;s? Looking at the structure of naphthalene, the intermolecular forces must be primarily London dispersion forces. Urea is capable of hydrogen bonding, so the intermolecular forces in solid urea are much stronger than the forces in solid naphthalene.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Finally, look at the results from the urea sample with the impurity. The melting point range should be broader and lower than the range for pure urea because of freezing point depression. As expected, the melting point range obtained was 127 &#8211; 130&#176;C, which is lower than the range for pure urea.</div>
		</li>
	</ul>
	</li>
</ol>

Determination of Melting Points - Procedure

熔点

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

	Determining the Melting Points of Naphthalene, Urea, and ...

Boiling Points

<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="">Boiling point determination of acetone and ethanol<button class="expand">Expand</button>
	<p>The temperature at which a pure organic substance changes from the liquid phase to the gas phase is known as the boiling point. A liquid&#39;s boiling point can be determined using the capillary method, where an inverted capillary is placed in the liquid of interest and the liquid is heated. As the temperature increases, the air in the capillary escapes and is replaced by the vapor of the liquid. The vapor pressure in the capillary increases with temperature. Once it exceeds the atmospheric pressure, the vapor escapes the capillary in a stream of bubbles. When the heat is removed, the liquid cools, and the vapor pressure in the capillary decreases. When the vapor pressure reaches the atmospheric pressure, the liquid begins to fill the capillary. The temperature at which this occurs is the boiling point.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-2">
		<div class="lab-step">Put on a lab coat, splash-proof safety glasses, and nitrile gloves. This experiment must be conducted in a hood.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Attach a small test tube to the thermometer using a rubber band, and secure the thermometer in the clamp.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Obtain acetone and bring it back to your hood. Using your glass pipette and a bulb, measure 1 mL of acetone and transfer it into the small test tube.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Align the thermometer end so that it is level with the acetone in the test tube, keeping them close to each other. Invert a capillary tube and place it in the test tube so that the open end is facing downwards.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Use a 250-mL beaker to create a water bath. Add approximately 180 mL of water to the beaker, and place it on the hotplate.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Lower the thermometer and test tube into the water bath. Turn on the hotplate to the lowest setting, about 30&#176;C.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Slowly increase the temperature on the hotplate by 10 &#8211; 20&#176;C every 10 min, and closely observe the liquid in the test tube. When you start to see occasional bubbles in the liquid, increase the heat setting by only 5&#176;C every 10 min.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Closely observe the capillary tube inside the test tube. Report the temperature at which a rapid and continuous stream of bubbles comes out of the capillary.
		<h4><strong>Table 1: Boiling point of acetone and ethanol</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td></td>
					<td colspan="2" style="text-align: center;"><strong>Boiling point temperature (&#176;C)</strong></td>
				</tr>
				<tr>
					<td></td>
					<td style="text-align: center;"><strong>Bubbles </strong></td>
					<td style="text-align: center;"><strong>Liquid in capillary </strong></td>
				</tr>
				<tr>
					<td>Acetone</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Ethanol</td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/57/Table_1._Boiling_point_of_acetone_and_ethanol.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Turn off the heat and allow the water bath to cool. Keep observing the capillary as the production of bubbles decreases until no bubbles emerge from the capillary. The liquid will start to rise in the capillary. Record the temperature at which this occurs.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Label a clean 25-mL beaker as &#8216;organic waste&#8217;. Once the water bath has cooled to about 35&#176;C, remove the thermometer and test tube from the bath. Detach the test tube from the thermometer and pour the acetone into the waste beaker.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Use a clean test tube and capillary and repeat the experiment using 1 mL of ethanol.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">After you have measured the boiling point of ethanol, allow the water bath to cool. Once it has cooled sufficiently, remove the test tube and thermometer from the water bath, detach the test tube from the thermometer, and pour the ethanol into the organic waste beaker.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Dispose of the water from the water bath down the sink and place the capillaries and test tubes in the glass disposal. Dispose of the organic waste in the container provided by your instructor.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Wash all of your glassware with detergent and water.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Results<button class="expand">Expand</button>
	<p>In this experiment, we measured the boiling point of acetone to be 56&#176;C, which compares well to the reported value. Similarly, the boiling point of ethanol was measured to be 78&#176;C. Errors in the boiling point measurement can be attributed to many experimental errors, such as heating the water bath too rapidly, or poor alignment of the thermometer and sample.</p>
	<p>The boiling point of an organic substance is directly related to its structure, where stronger intramolecular forces result in a higher boiling point as molecules are able to hold onto each other and remain in the liquid phase longer. The higher boiling point for ethanol is observed due to the OH structure that causes hydrogen bonding between the molecules. Acetone has a polar CO double bond, which results in dipole-dipole forces. Since hydrogen bonding is stronger than dipole-dipole forces, ethanol has a higher boiling point.</p>
	<p>Additionally, ethanol has a lower molecular weight than acetone. However, molecular weight has less of an impact on the boiling point than the molecular structure. For example, butane is a gas at room temperature and pressure, as it has a boiling point lower than 25&#176;C. Ethanol has a slightly lower molecular mass than butane, but it is liquid at room temperature and, therefore, has a boiling point higher than room temperature. This is due to the hydrogen bonding between the ethanol molecules, which is stronger than the van der Waals forces between the butane molecules.</p>
	<ul class="lab-items">
	</ul>
	</li>
</ol>

Determination of Boiling Points by Capillary Method - Procedure

沸点

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

	Boiling point determination of acetone and ethanolExpand
	...

Recrystallization

<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="">Recrystallization of Acetanilide<button class="expand">Expand</button>
	<p>In this part of the lab, you&#39;ll purify acetanilide by recrystallization from an aqueous solution. Acetanilide is moderately soluble in boiling water, but it&#39;s much less soluble in room temperature and cold water. Aniline, a potential impurity, is much more soluble in room temperature water. Thus, you&#39;ll first make a saturated solution of acetanilide in boiling water. Then, you&#39;ll slowly cool the solution to room temperature.</p>
	<p>As the acetanilide&#39;s solubility decreases, it will slowly form flat colorless or white crystals. Water-soluble impurities will remain in solution. You will then cool the solution to further decrease the solubility of acetanilide. Finally, you&#39;ll recover the crystals with vacuum filtration and measure the melting point of your crystals.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-3">
		<div class="lab-step">Before you start the lab, put on a lab coat, safety glasses, and nitrile gloves.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">To begin, bring a 125-mL Erlenmeyer flask and your lab notebook to the analytical balance to obtain your acetanilide.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Measure 2 g of acetanilide in a tared weighing boat and record the precise mass in your lab notebook. Add the acetanilide to the flask and bring it back to your fume hood.
		<h4><strong>Table 1: Recrystallization of acetanilide</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td><strong>Compound</strong></td>
					<td><strong>Mass (g) </strong></td>
					<td><strong>Melting point (&#176;C) </strong></td>
				</tr>
				<tr>
					<td>Acetanilide</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Seed crystal (if used)</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Recrystallized acetanilide<br />
					(<em>subtract seed crystal if used</em>)</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td><strong>Percent recovery</strong></td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/58/Table_1._Recrystallization_of_acetanilide.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Then, measure 30 mL of deionized water and carefully pour it into the flask of acetanilide.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Place the flask on a stirring hotplate, add a stir bar, and set the hotplate to medium heat and stirring. Let the mixture boil for 4 &#8211; 5 min to dissolve the acetanilide.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">If you see solid acetanilide after the solution has boiled for 5 min, measure another 10 mL of deionized water. Use a Pasteur pipette to add water dropwise until either the solid dissolves or you&#39;ve added all 10 mL.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Let the solution boil for at least a minute after each milliliter before adding more water.<strong> Note:</strong> It&#39;s important to add water slowly so that you don&#39;t cool the solution too much or add more water than you need.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">If you still see some solid after that, those are impurities that you must remove by hot filtration. If you do not see solid, continue the lab at step 14.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">To perform hot filtration, place about 15 mL of deionized water and one or two boiling chips in a 50-mL beaker and start heating it on a hotplate.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Clamp another 125-mL Erlenmeyer flask on a hotplate and place a wide stem or stemless glass funnel in the flask. Fold a large piece of circular filter paper in quarters, place it point down in the funnel, and open it into a cone.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Once the water boils, use a pipette to wet the filter paper with hot water. Then, use tongs to pick up the flask of acetanilide solution and pour the hot liquid into the funnel, being careful not to let it overflow. <strong>Note:</strong> If the stir bar falls into the funnel, retrieve it with tweezers and rinse it with hot water.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Then, rinse the inside of the first flask with a few milliliters of hot water, pour the contents into the funnel, and dissolve any crystals that form with hot water.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Once the funnel is empty, use tongs to move it to the first flask. Carefully unclamp the second flask. You can now continue with the lab as usual.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Once there is no visible solid in your hot acetanilide solution, turn off the heat and stir motor and use tongs to place the flask on the floor of the hood.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Leave the solution undisturbed as it cools to room temperature, which usually takes at least 15 min. Moving or shaking the flask will make it harder for crystals to form.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">While you wait, place a small amount of the starting acetanilide material in a weighing boat and bring it to the melting point apparatus.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Pack a capillary tube with the acetanilide and measure and record its melting point.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Once the solution cools, look for crystals without moving the flask too much. If you don&#39;t see any, use a glass rod to gently scratch the inside of the flask under the solution. It&#39;s easier for crystals to start to form on scratched or rough surfaces.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">If crystals still haven&#39;t formed after 10 more min, ask your instructor for a seed crystal of high purity acetanilide. Measure and record the mass of the seed crystal, and then drop it into the room temperature acetanilide solution. Crystal growth will then occur on the seed crystal.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">Once you see several crystals in the flask, prepare two ice baths in 600-mL beakers. One ice bath should nearly fill the beaker, and the other should occupy about half of the beaker.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Measure 5 mL of deionized water and place it in the full ice bath. Confirm that the flask is cool to the touch and that several crystals have formed before gently placing it in the half-full ice bath. Leave the flask undisturbed to improve crystal growth.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Check the crystal growth progress every 15 min. Once it looks like most of your acetanilide has crystallized, or you don&#39;t see much crystal growth over a 15-min period, set up for a vacuum filtration using a 125- or 250-mL filter flask.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Wet the filter paper with 1 mL of ice-cold water. Then, start the vacuum and pour the contents of the flask into the B&#252;chner funnel of the vacuum filtration setup.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Scrape crystals from the flask into the funnel using a glass rod or flexible spatula and rinse the remaining crystals into the funnel with about 1 mL of cold deionized water.</div>
		</li>
		<li data-sub-note-item="1-27">
		<div class="lab-step">Then, stop the vacuum, break the seal, and pour the rest of the cold deionized water into the funnel. Gently stir the crystals with the glass rod for a few seconds to wash them, being careful not to tear the filter paper.</div>
		</li>
		<li data-sub-note-item="1-28">
		<div class="lab-step">Turn on the vacuum to drain the funnel. Then, stop the vacuum, break the seal, and empty the filtrate into a waste beaker. Turn the vacuum back on, and leave the washed crystals in the funnel while the vacuum pump pulls air through them until they are dry, which usually takes about half an hour. You&#39;ll start working on your next recrystallization while you wait.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Recrystallization of <em>trans</em>-Cinnamic Acid<button class="expand">Expand</button>
	<p>In the second half of the lab, you&#39;ll recrystallize <em>trans</em>-cinnamic acid, which we&#39;ll just call cinnamic acid. Cinnamic acid is soluble in ethanol and nearly insoluble in water. So, you&#39;ll use a mixture of 95% ethanol and 5% water so that cinnamic acid is still soluble at high temperatures but less soluble at low temperatures.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-2">
		<div class="lab-step">To get started, fill a 5- or 10-mL graduated cylinder with deionized water and bring it to your hood.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Then, weigh 0.5 g of cinnamic acid, record its mass, and place it in a 25-mL Erlenmeyer flask.
		<h4><strong>Table 2: Recrystallization of<em> trans</em>-Cinnamic acid</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td><strong>Compound</strong></td>
					<td><strong>Mass (g) </strong></td>
					<td><strong>Melting point (&#176;C) </strong></td>
				</tr>
				<tr>
					<td><em>trans</em>-Cinnamic acid</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Seed crystal (if used)</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Recrystallized<em> trans</em>-cinnamic acid<br />
					<em>(subtract seed crystal if used)</em></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td><strong>Percent recovery</strong></td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/58/Table_2._Recrystallization_of_trans-Cinnamic_acid.xlsx" target="_blank">Click Here to download Table 2</a></div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Next, obtain 4 mL of 95% ethanol, and pour it into the flask containing cinnamic acid. Place the flask on a hotplate set to medium heat and stir the solution with a glass rod until the cinnamic acid dissolves, which usually takes 7 &#8211; 10 min.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Then, turn off the heat and use a Pasteur pipette to add 5 drops of deionized water to the solution. This reduces cinnamic acid solubility. <strong>Note:</strong> If you don&#39;t see precipitation, add up to 5 more drops of water one by one. Stop adding water if you see solids starting to form.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Then, remove the flask from the hotplate and let it cool to room temperature undisturbed.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">While you wait, get a small amount of the starting cinnamic acid and measure its melting point.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Once the flask has cooled to room temperature, inspect it for crystals. If you don&#39;t see any, gently scratch the inside of the flask under the solution with the glass rod and wait for 10 min. <strong>Note:</strong> If that still doesn&#39;t work, get a seed crystal of cinnamic acid from your instructor. Remember to weigh the seed crystal and record its mass before you add it to your solution.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Once the flask is cool to the touch and contains several crystals, remake the ice baths with one ice bath shallow enough that the 25-mL flask will not be completely submerged.</div>
		</li>
		<li data-sub-note-item="2-10">
		<div class="lab-step">Refill the graduated cylinder with deionized water. Place the flask of cinnamic acid crystals in the shallow ice bath and the water-filled graduated cylinder in the other ice bath. Let the crystals grow for at least 15 min.</div>
		</li>
		<li data-sub-note-item="2-11">
		<div class="lab-step">Your acetanilide crystals should be dry by now, so measure their mass and melting point while you wait for your cinnamic acid to finish crystallizing. Turn off the vacuum and break the vacuum seal.</div>
		</li>
		<li data-sub-note-item="2-12">
		<div class="lab-step">Gently place the B&#252;chner funnel in a clean beaker and bring it to the balance. Measure and record the mass of your pure acetanilide crystals. Remember to subtract the mass of the seed crystal if you used one.</div>
		</li>
		<li data-sub-note-item="2-13">
		<div class="lab-step">Then, bring your crystals to the melting point apparatus and measure and record the melting point.</div>
		</li>
		<li data-sub-note-item="2-14">
		<div class="lab-step">Now, place a clean, dry B&#252;chner funnel with a new piece of filter paper in the filter flask and check on your cinnamic acid. Once it looks like most of the cinnamic acid has crystallized, wet the filter paper with cold deionized water.</div>
		</li>
		<li data-sub-note-item="2-15">
		<div class="lab-step">Start the vacuum and pour the contents of the cinnamic acid flask into the funnel. Scrape the remaining crystals out of the flask with the glass rod and rinse the flask with about 1 mL of cold water.</div>
		</li>
		<li data-sub-note-item="2-16">
		<div class="lab-step">Now, turn off the vacuum, break the seal, and pour the rest of the cold water into the funnel. Gently stir the crystals with the glass rod to wash them, being careful not to damage the filter paper.</div>
		</li>
		<li data-sub-note-item="2-17">
		<div class="lab-step">Turn on the vacuum to drain the funnel. Leave the vacuum running until the cinnamic crystals are dry.</div>
		</li>
		<li data-sub-note-item="2-18">
		<div class="lab-step">Place the B&#252;chner funnel in a beaker and bring it to the balance. Measure and record the mass of your pure cinnamic acid crystals. Remember to subtract the mass of the seed crystal if you used one. Then, measure the melting point of your recrystallized cinnamic acid.</div>
		</li>
		<li data-sub-note-item="2-19">
		<div class="lab-step">Now, dispose of your acetanilide and cinnamic acid in the designated solid waste container. Flush the filtrate down the drain with running water and pour leftover ice and water into the sink.</div>
		</li>
		<li data-sub-note-item="2-20">
		<div class="lab-step">Clean your glassware using your usual methods and put away your other lab equipment.</div>
		</li>
		<li data-sub-note-item="2-21">
		<div class="lab-step">Lastly, discard your used pipettes in the glass waste and throw out used filter paper and other trash in the lab trash container.</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, calculate the percent recovery for each compound. We expect that some of each compound stayed in solution, so these percentages will be below the reported purity of your starting material.</div>
		</li>
		<li data-sub-note-item="3-2">
		<div class="lab-step">Now, look at the differences in melting points between the starting material and the crystals. For each compound, the less pure starting material has a lower melting point and a broader range than the recrystallized compound.</div>
		</li>
		<li data-sub-note-item="3-3">
		<div class="lab-step">Lastly, compare your results to the literature values. The melting point of acetanilide is 114 &#176;C, and the melting point of <em>trans</em>-cinnamic acid is 133 &#176;C. The melting points of your crystals should span 1 &#8211; 2 &#176;C and should be at or just below those values.</div>
		</li>
	</ul>
	</li>
</ol>

Recrystallization of Acetanilide and trans-Cinnamic Acid - Procedure

重结晶

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

	Recrystallization of AcetanilideExpand
	In this part of ...

Simple 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="">Simple Distillation<button class="expand">Expand</button>
	<p>In this lab, you will use simple distillation to separate a mixture of cyclohexane and toluene.</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 conducted in a hood.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Assemble the distillation apparatus. Refer to the example set up that has been prepared by your instructor.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Then, set up the two stands next to each other in the hood. Place the magnetic stirrer on the base of one of the stands.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Set the heating mantle on top of the magnetic stirrer, and then plug it into the temperature controller.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Add 5 &#8211; 10 mL of sand to the heating mantle. This will allow more homogeneous heating of the round-bottom flask. Clamp the round-bottom flask to the stand above the heating mantle.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Now, obtain cyclohexane and toluene from your instructor. Measure 2 mL of cyclohexane using a volumetric pipette and dispense it into the round-bottom flask.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Then, use a clean volumetric pipette to measure 2 mL of toluene and add it to the flask.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Carefully insert a thermometer into an adapter by gently pushing and twisting it through the top.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Lightly grease the adapter with vacuum grease and insert it into the distilling head. Make sure that the thermometer bulb is below the bend of the distilling head. Then, lightly grease the joints of the distilling head.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Add a stir bar to the round-bottom flask and insert the distilling head into the round-bottom flask.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Now, clamp the condenser to the second stand with it oriented diagonally toward the side joint of the distilling head.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Connect one piece of tubing to the tap water faucet in the hood, and attach the other end to the inlet port of the condenser, which is located farthest from the distilling head.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Attach the second tubing to the outlet port, which is located closest to the distilling head, and place the other end of the tubing into the drain.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Connect the condenser to the distilling head. Then, lightly grease the joint of the condenser and attach the connecting tube. Place a 10-mL graduated cylinder below the outlet of the tube.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Gently lower the setup until the round-bottom flask is seated in the sand in the heating mantle.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Double-check all of the connections on your setup to make sure that they are tight and oriented correctly. Secure each joint with a plastic clip.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Now, slowly turn on the flow of water to the condenser. <strong>Note:</strong> Be careful not to turn on the water too quickly. If the water pressure is high, the tubing may pop off the condenser.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Turn the magnetic stirrer to the lowest setting, and set the temperature controller to heat the mantle to just above 90 &#176;C.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Once bubbles start forming in the liquid mixture, adjust the heat until the distillation rate is about 2 drops/min. You should also see drops forming on the thermometer bulb.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Record the temperature after every 2 drops that fall into the graduated cylinder or every minute.
		<h4><strong>Table 1: Distillation of toluene and cyclohexane</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td><strong>Time (min) </strong></td>
					<td><strong>Distilled volume (mL) </strong></td>
					<td><strong>Temperature (&#176;C) </strong></td>
				</tr>
				<tr>
					<td style="text-align: center;">1</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;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">3</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">4</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">5</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">6</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">7</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">8</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">9</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">10</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">11</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">12</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">13</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">14</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td style="text-align: center;">15</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/60/Table_1._Distillation_of_toluene_and_cyclohexane.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">When there is about 0.5 mL of the mixture remaining in the flask, which will look like a thin layer of liquid, turn off the heat and gently lift the glassware setup from the heating mantle. <strong>Note:</strong> Never heat the mixture until the flask is dry as this may cause an explosion.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Remove the stir plate with the heating mantle and set it aside.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Then, turn off the water to the condenser and allow the setup to cool completely. When it is cool, carefully disassemble the glassware.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Dispose of all solutions in the non-halogenated organic waste container. Clean your glassware with acetone followed by detergent and deionized water.</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">Plot the dew point temperature versus the distilled volume during the experiment. We see that drops start to fall into the collection vessel at ~ 81 &#176;C, which is the boiling point of cyclohexane. As the distillation progresses, the temperature increases to almost 111 &#176;C, which is the boiling point of toluene.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Early in the distillation, the vapor is rich in cyclohexane. As the second milliliter is distilled, the temperature increases by ~ 20 &#176;C, which tells us that the amount of toluene in the vapor is increasing significantly. The temperature stabilizes as it approaches 111 &#176;C, which tells us that the vapor is rich in toluene towards the end of the distillation.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Look at a boiling point diagram for cyclohexane and toluene, with the mole percent of cyclohexane and toluene on the x-axis and the temperature on the y-axis. The solid line denotes the bubble point, and the dashed line denotes the dew point.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Use the dew point curve to determine the composition of the vapor throughout the distillation. For example, after 0.5 mL has been distilled, the condensing vapor is about 84 &#176;C. This corresponds to 95% cyclohexane on the dew point curve.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Once you know the composition of the vapor at each point, estimate the composition of the boiling mixture throughout the distillation. At room temperature, cyclohexane and toluene have nearly the same number of moles per milliliter, so think of the percentages in terms of volume.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">To determine how much of each liquid was distilled in each step, apply each percentage to the volume of liquid distilled since the previous measurement. This tells us that we distilled 1.9 mL of cyclohexane and 1.1 mL of toluene from our mixture of 2 mL of each liquid. Thus, our distillate was 63% cyclohexane and 37% toluene, and our remaining liquid mixture was 10% cyclohexane and 90% toluene.</div>
		</li>
	</ul>
	</li>
</ol>

Simple Distillation: Separation of a Mixture of Cyclohexane and Toluene - Procedure

简单蒸馏

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

	Simple DistillationExpand
	In this lab, you will use ...