<p class="jove_content">We thank Miss. Hirakawa for her great contribution to this research.</p>

<p class="jove_content">NOTE: Please check all related material safety data sheets (MSDS). Please wear protective equipment when experimenting with the copper sulfate plating.</p>
<p class="jove_title">1. Preparation of the copper sulfate plating solution</p>
<p class="jove_content">NOTE: The copper sulfate plating aqueous solution is prepared by combining sulfuric acid (0.5 mol/L), copper sulfate (0.4 mol/L), chlorine (Cl, 1.41 mmol/L), polyethylene glycol (PEG; MW 4000: 0.025 mmol/L), bis(3-sulfopropyl) disulfide (SPS, 0.003 mmol/L), and Janus Green B (JGB, 0.004 mmol/L) in pure water.</p>
<ol>
	<li>Place a stir bar in a 1 L beaker and pour in 600 mL of pure water. Add sulfuric acid (95.0%: 49.04 g) in small portions while stirring. Leave it until the solution cools down.</li>
	<li>Add copper sulfate (99.5%: 99.876 g) to the solution little by little. Stir for 30 min.</li>
	<li>Add 23.7 mL of hydrochloric acid (0.02 mol/L), 0.1 g of polyethylene glycol, 1 mL of 1 mg/L SPS solution, and 1 mL of 2 mg/L JGB solution.</li>
	<li>Transfer the solution to a volumetric flask (1 L). Add pure water and adjust to 1 L. Transfer the copper sulfate plating solution to a polyethylene container and store it at room temperature in the dark.</li>
</ol>
<p class="jove_title">2. Formation of the Cu(I) in the plating solution</p>
<ol>
	<li>Pour 150 mL of the copper sulfate plating solution into a 200 mL beaker. Put the stir bar in the beaker and stir at 500 rpm. Leave the plating solution in advance at room temperature (23 &#176;C &#177; 1 &#176;C) for 1 hour.</li>
	<li>Insert a tube into a beaker and let nitrogen flow (about 85 mL/min). Deoxygenate the plating solution with nitrogen gas for over 30 min.</li>
	<li>Cut the 0.3 mm thick copper plate with metal shears to 9.5 cm x 2 cm dimensions. Cut the platinum plate with a thickness of 0.1 mm in the same way.</li>
	<li>Wash the copper plate and the platinum plate with ethanol and rinse with pure water. Dry with nitrogen gas.</li>
	<li>Attach the copper plate and platinum plate to the fixing jig, insert it inside the beaker and fix it. The immersed area of each plate to the plating solution is 4 x 2 cm<sup>2</sup> (See <strong class="xfig">Figure 2</strong>).<br />
	NOTE: The jig consists of an acrylic beaker fixing part (<strong class="xfig">Figure 3</strong> (1)) and metal electrode parts (<strong class="xfig">Figure 3</strong> (2)). The electrode part consists of the parts to fix the plate, and the part connects to the cord from the power supply.</li>
	<li>Connect the electrode (anode) of the copper plate to the positive end of the power supply (<strong class="xfig">Figure 3</strong> (3)), and the electrode of the platinum plate (cathode) to the negative end of the power supply (<strong class="xfig">Figure 3</strong> (4)).</li>
	<li>Turn on the power supply at a constant current of 1.0 A (current density: 62.5 mA/cm<sup>2</sup>). Cu(I) is formed in the plating solution according to the electrolysis time, and Cu(I) concentration (accumulated amount) is maximized in about 10 min.<br />
	NOTE: If the plate is inserted while the stirrer rotates, the plating solution may scatter and the beaker may fall over. Please install the jig before turning on the power to avoid danger.</li>
	<li>Turn off the power after 10 min and stop the stirrer. Leave it for about 10 min until the particles settle.</li>
</ol>
<p class="jove_title">3. Quantitative measurement of the Cu(I)</p>
<ol>
	<li>Prepare the BCS solution (10<sup>-2</sup> mol/L) by dissolving 0.36 g of the molecule in 100 mL of pure water. Stir the solution and dissolve the BCS in an excess amount relative to the monovalent copper. Store the BCS solution in a light-proof container and store the container in the dark.<br />
	NOTE: In the measurement, the BCS concentration in the sample solution is adjusted to 1,000 times or more the Cu(I) concentration.</li>
	<li>Add 60 mL of acetic acid (1 mol/L) and 25.2 mL of NaOH solution (1 mol/L) to 120 mL of pure water to prepare a neutralizing solution (buffer solution).</li>
	<li>Put a stir bar in the absorption measurement cell (optical path length: 1 cm) and pour in 2.5 mL of neutralization solution and 219 &#956;L of BCS solution.</li>
	<li>Mix in 22 &#956;L of plating solution sample (step 2.9). Stir for 20 min.<br />
	NOTE: In order to ensure that the function of BCS is normal, the pH of the sample solution to be measured should not fall below 4. BCS selectively forms a complex with Cu(I). The Cu(I)-BCS complex absorbs in the visible region (400 to 550 nm), and the neutralizing solution develops an orange color (<strong class="xfig">Figure 4</strong>).</li>
	<li>Measure the absorption spectra of the sample solution (3.4) with an UV/vis spectrophotometer (wavelength range: 400&#8211;600 nm) (<strong class="xfig">Figure 5e</strong>).<br />
	NOTE: There are no constrained measurement apparatus and conditions, and it is desirable to make them identical in one experiment series.</li>
	<li>Calculate the concentration of Cu(I) using the Lambert-Beer law:<br />
	A = &#949;<em>l</em>c<br />
	where A is absorbance, L is the optical path length, &#949; is the molar absorption coefficient (BCS: 1.2 &#215; 10<sup>4</sup> at 485 nm), and c is the molar concentration (mol/L) of the solute.<br />
	NOTE: Because the optical path length is 1 cm, the Cu(I) concentration in the cell is simply the absorbance divided by the molar extinction coefficient. The value obtained by multiplying the ratio 125 (the fold dilution with the neutralizing solution) is the Cu(I) concentration of the plating solution.</li>
</ol>
<p class="jove_title">4. Injection measurement of Cu(I) and BCS color reaction curves</p>
<ol>
	<li>Use a UV/vis spectrophotometer with time measurement function of more than 20 min for injection measurement. The spectrometer should have a sample chamber cover with a syringe port (<strong class="xfig">Figure 6</strong> left) and a thermostat cell holder with a stirrer.</li>
	<li>Use a square cell of 1 cm x 1 cm for the absorbance measurement. Put s stir bar in the absorption cell.</li>
	<li>Pour 2.5 mL of the neutralized solution prepared in 3.2 and 219 &#956;L of the BCS solution prepared in 3.1 into the cell. Maximize stirrer rotation speed.</li>
	<li>Set the measurement time to 1,270 s in the time measurement mode at 485 nm and start. One min after starting, inject 22 &#956;L of the plating solution sample (2.9) with a pipette from the syringe port of the chamber cover. Reaction curves of Cu(I) and BCS will be acquired (<strong class="xfig">Figure 6</strong> right).</li>
</ol>

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	<li>Kondo, K., Akolkar, R. N., Barkey, D., Yokoi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chap+1.">Chap 1.</a> <em style='font-style: italic'>Copper Electrodeposition for Nanofabrication of Electronics Devices</em>. , (2014).</li><li>Kondo, K., Nakamura, T., Okamoto, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+between+Cu+(I)-complexes+and+filling+of+via+cross+section+by+copper+electrodeposition.">Correlation between Cu (I)-complexes and filling of via cross section by copper electrodeposition.</a> <em style='font-style: italic'>Journal of Applied Electrochemistry</em>. <b>39</b>, 1789-1795 (2009).</li><li>Healy, J. P., Pletcher, D., Goodenough, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Chemistry+of+the+additives+in+an+acid+copper+electroplating+bath,+Part+II.+The+instability+of+4,5-dithiaoctance-1,8-disulphonic+acid+in+the+bath+on+open+circuit.">The Chemistry of the additives in an acid copper electroplating bath, Part II. The instability of 4,5-dithiaoctance-1,8-disulphonic acid in the bath on open circuit.</a> <em style='font-style: italic'>Journal of Electroanalytical Chemistry</em>. <b>338</b>, 167-177 (1992).</li><li>Frandon, E. E., Walsh, F. C., Campbell, S. 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<p class="jove_content">We have nothing to disclose.</p>

<p class="jove_content"><strong class="xfig">Figure 2</strong> schematically shows a system for electrolysis experiment. The jig is an ordered item, which consists of an acrylic part to be fixed to beakers and metal parts for attaching plates and for connecting with the power supply. By this mechanism, the immersion area of the plates becomes constant, and the relationship between the current value and the current density is kept constant. In our conditions, immersion is 4 cm x 2 cm, and the current density will be 62.5 mA/cm<sup>2</sup> with a current of 1 A. In the accumulation procedure of Cu(I), a copper plate is attached to the anode and a platinum plate is attached to the cathode. In order to increase the accumulation efficiency of Cu(I), it is preferable to deoxidize the plating solution with nitrogen gas beforehand.</p>
<p class="jove_content">Quantitative measurement of Cu(I) consists of a simple procedure. Pour the neutralization solution and BCS solution into the cell and mix the plating solution (<strong class="xfig">Figure 4</strong>). It is necessary to stir for more than 20 min until Cu(I) and BCS react sufficiently. This is to ensure the accuracy of the measurement by sufficiently advancing the reaction. If Cu(I) is contained in the plating solution, the sample solution appears orange and an absorption spectrum having a peak at 485 nm is obtained. Changes in solution color due to the complex formation were dramatic and surprised many copper plating technicians.</p>
<p class="jove_content">It is confirmed that Cu(I) accumulates in the solution when a current is passed through the copper sulfate plating solution (<strong class="xfig">Figure 5</strong>). The absorption spectrum shows the shape of the Cu(I)-BCS complex, which is suitable for calculating the Cu(I) concentration from the absorbance at 485 nm. Although the current value is arbitrary, Cu(I) is hardly accumulated at a current value of 0.2 A, and a higher current value is required. Although the accumulation amount of Cu(I) tends to increase with electrolysis time, it is saturated by excessive current (for example, electrolysis for more than 10 min at 1.0 A). The accumulation amount of Cu(I) increased by electrolysis for 10 min when the current value was 0.5 to 1.0 A<sup class="xref">14</sup>. When an excessive current flowed (for example, at 1.0 A for 20 min), the Cu(I) concentration decreased. This is thought to be related to the formation of copper particles due to the progress of the disproportionate reaction.</p>
<p class="jove_content">The reaction of Cu(I) and BCS in the plating solution has multiple time components, which often make the accurate determination of the concentration difficult. In order to solve this problem, an injection measurement is desirable (<strong class="xfig">Figure 6</strong>). In this measurement, the absorption intensity of the Cu(I)-BCS complex is acquired as a changed amount from the baseline before injection of the plating solution, so it can be determined more accurately. In addition, since the reaction curve can be simply numerically analyzed, the concentration can be known with high accuracy even if the reaction is not completed. The components of the reaction curve are thought to reflect the retention structure of Cu(I) in the plating solution<sup class="xref">14</sup>.</p>
<p class="jove_content">It is important to model the holding structure of Cu(I) in the plating solution against the assertion that Cu(I) in the plating bath instantaneously oxidizes Cu(II). We propose the following model from analysis of characteristics of the current amount, formation, and accumulation of Cu(I). A portion of the Cu(I) eluted from the copper plate is retained in solution in the form of a Cu(I)-PEG complex. In early stages of the complex formation, chloride ions are thought to play a role as a temporary stabilizer for Cu(I)<sup class="xref">6</sup><sup>,</sup><sup class="xref">8</sup>. Cu(I) coordinated to PEG is incorporated inside the three-dimensional structure, and it is in a hydrophobic environment. When the formation of Cu(I) is promoted, excess Cu(I) is coordinated to the surface of the PEG and may be in the vicinity of the liquid. Since Cu(I) on the surface reacts promptly with BCS, it will reflect the A0 component of the reaction curve. Since the Cu(I) inside the PEG is protected from BCS attack, it has a slow AL component. It has been pointed out that the A0 component mainly influences the quality of the plating film<sup class="xref">15</sup>. This information is important for management of the plating solution.</p>
<p class="jove_content">By accelerating the denaturation of the plating solution and verifying the accumulated Cu(I) concentration and the holding structure, it is possible to clearly characterize the plating solution. This is important not only for understanding the plating process but also for predicting the quality of the plating film to be produced. From the verification of the SEM image, it was shown that the Cu(I) concentration, especially the A0 component, is strongly involved in the generation of the roughness of the plating film (<strong class="xfig">Figure 8</strong>). On-site measurement of Cu(I) gives new indications for the management of plating baths.</p>
<p class="jove_content">This research can contribute to the management of the plating bath based on optical measurement. We aim to develop a system that can evaluate the state of the plating bath on the production line on-time and in situ.</p>

<p class="jove_content">As printed circuit boards become denser and multilayered, management of plating solutions during the manufacturing process becomes more important to maintain product quality. In copper sulfate electroplating, the monovalent copper ion (cuprous ion: Cu(I)) has been determined to be one of the main causes of the large roughness and dull finish of the copper plating surface. The behavior and role of Cu(I) in the plating process<sup class="xref">1</sup><sup>,</sup><sup class="xref">2</sup><sup>,</sup><sup class="xref">3</sup><sup>,</sup><sup class="xref">4</sup><sup>,</sup><sup class="xref">5</sup>, the effect of each additive, and the holding structure<sup class="xref">6</sup><sup>,</sup><sup class="xref">7</sup><sup>,</sup><sup class="xref">8</sup> have been investigated. It is necessary to analyze Cu(I) in the plating solution, but it was difficult to quantify its concentration because of the instability of Cu(I) in an aqueous solution. Therefore, the on-site analysis of Cu(I) in the plating bath is an effective tool for controlling the plating solution.</p>
<p class="jove_content">We performed colorimetric analysis using an aqueous chelating reagent, BCS (bathocuproinedisulfonic acid, disodium salt), to establish on-site quantitative analysis of Cu(I) in a copper sulfate plating solution. The BCS can be used to quantify the Cu(I) concentration in the aqueous solutions<sup class="xref">9</sup><sup>,</sup><sup class="xref">10</sup><sup>,</sup><sup class="xref">11</sup>. The cuproine type color reaction reagent, which has been conventionally used for the determination of Cu(I), is hydrophobic and extraction with alcohol is necessary. It was shown that BCS is hydrophilic and can directly measure Cu(I) in an aqueous solution. Two molecules of BCS coordinate to one Cu(I) to form 1:2 complexes that absorb visible light at wavelengths between 400 and 550 nm (See <strong class="xfig">Figure 1</strong>). We established a method to determine the concentration of Cu(I) in the plating solution from the measurement of the absorbance of the Cu(I)-BCS complex<sup class="xref">12</sup><sup>,</sup><sup class="xref">13</sup>. In the first part of this protocol, a method of accelerating the Cu(I) formation in a copper sulfate plating solution in a model experimental system and the quantitative measurement of the Cu(I) concentration in a plating solution are described. This is fundamental to clarify the process of formation and accumulation of Cu(I) in the plating bath.</p>
<p class="jove_content">Further, it was shown that the color reaction of Cu(I) and BCS can be divided into rapid reaction components and relatively slow reaction components. This increases the uncertainty in the absorbance measurement. To overcome this problem, we developed a method of measuring reaction curves by an injection method<sup class="xref">14</sup><sup>,</sup><sup class="xref">15</sup>. The second part shows the measurement of Cu(I) based on the injection method. By analyzing the components obtained by the injection method, it is possible to approximate the understanding of the Cu(I) formation mechanism and holding structure in solution.</p>
<p class="jove_content">Conventionally, it has been claimed that Cu(I) in a plating solution is instantly oxidized to cupric ions (Cu(II)). We have confirmed that there are several millimoles (mmol/L) of Cu(I) in the plating bath of the production line<sup class="xref">12</sup>. According to this experiment method, the accumulation of Cu(I) similar to the plating bath can be reproduced even in the beaker of the laboratory. This is a fundamental technology to elucidate the Cu(I) production and accumulation process in a copper sulfate electroplating solution, which was unknown<sup class="xref">14</sup>. Furthermore, by controlling Cu(I) in the plating solution, it is also possible to predict the effect of Cu(I) on the quality of the plating film<sup class="xref">15</sup>.</p>

<table><tbody><tr><td>Acetic acid</td><td>Wako</td><td>016-18835</td><td></td></tr><tr><td>BCS</td><td>Dojindo</td><td>B002</td><td></td></tr><tr><td>Copper plate</td><td>YAMAMOTO-MS</td><td>B-60-P05</td><td></td></tr><tr><td>Copper sulfate</td><td>Wako</td><td>033-04415</td><td></td></tr><tr><td>Hydrochorinic acid</td><td>SIGMA-ALDRICH</td><td>13-1750-5</td><td></td></tr><tr><td>JGB</td><td>Wako</td><td>106-00011</td><td></td></tr><tr><td>Magnetic stirrer</td><td>Iuchi</td><td>HS-30D</td><td></td></tr><tr><td>NaOH</td><td>NACALAI TESQUTE</td><td>31511-05</td><td></td></tr><tr><td>PEG4000</td><td>Wako</td><td>162-09115</td><td></td></tr><tr><td>Platinum plate</td><td>NILACO</td><td>PT-353326</td><td></td></tr><tr><td>Power supply</td><td>TAKASAGO</td><td>LX018-28</td><td></td></tr><tr><td>SPS</td><td>Wako</td><td>327-87481</td><td></td></tr><tr><td>Stir bar</td><td>AS ONE</td><td>1-5409-01</td><td></td></tr><tr><td>Sulfuric acid</td><td>Wako</td><td>192-04696</td><td></td></tr><tr><td>Syringe port</td><td>JASCO</td><td>CSP-749</td><td></td></tr><tr><td>Thermostat cell holder with a stirrer</td><td>JASCO</td><td>STR-773</td><td></td></tr><tr><td>UV/vis Spectrophotometer</td><td>JASCO</td><td>V-630</td><td></td></tr></tbody></table>

accumulation and analysis of cuprous ions in a copper sulfate plating solution

<p class="jove_content">Knowledge of the behavior of cuprous ions (monovalent copper ion: Cu(I)) in a copper sulfate plating bath is important for improving the plating process. We successfully developed a method to quantitatively and easily measure Cu(I) in a plating solution and used it for evaluation of the solution. In this paper, a quantitative absorption spectrum measurement and a time-resolved injection measurement of Cu(I) concentrations by a color reaction are described. This procedure is effective as a method to reproduce and elucidate the phenomenon occurring in the plating bath in the laboratory. First, the formation and accumulation process of Cu(I) in solution by electrolysis of a plating solution is shown. The amount of Cu(I) in the solution is increased by electrolysis at higher current values &#8203;&#8203;than the usual plating process. For the determination of Cu(I), BCS (bathocuproinedisulfonic acid, disodium salt), a reagent that selectively reacts with Cu(I), is used. The concentration of Cu(I) can be calculated from the absorbance of the Cu(I)-BCS complex. Next, the time measurement of the color reaction is described. The color reaction curve of Cu(I) and BCS measured by the injection method can be decomposed into an instantaneous component and a delay component. By analysis of these components, the holding structure of Cu(I) can be clarified, and this information is important when predicting the quality of the plating film to be produced. This method is used to facilitate the evaluation of the plating bath in the production line.</p>

<p class="jove_content" fo:keep-together.within-page="1">The concentration of Cu(I) in the plating solution can be determined from the absorbance at 485 nm of Cu(I)-2BCS chelate. <strong class="xfig">Figure 5</strong> shows the absorption spectra of the plating solutions that were electrolyzed for 0, 4, 6, 8 and 10 min. The Cu(I) concentration tends to increase from 0 to 10 min depending on the electrolysis time. However, as a result of the time-resolved measurement, a delay component appeared in addition to the instantaneous component in the reaction between BCS and Cu(I). This reduces the signal-to-noise ratio (S/N ratio) of the absorbance value and prevents accurate determination of Cu(I) concentration. It is preferable to use the injection method to determine the Cu(I) concentration, because the change in absorbance caused by the injection of plating solution is measured by time decomposition (<strong class="xfig">Figure 6</strong>).</p>
<p class="jove_content" fo:keep-together.within-page="1">Information on the Cu(I) holding structure in the plating solution is obtained by numerical analysis of the reaction curve. In general, Cu(I) is quickly oxidized to Cu(II) in an aqueous solution; but in the plating solution it is considered to be stabilized by forming a complex with an additive (especially PEG)<sup>14</sup>. The reaction curve reflects the chelation process of Cu(I) and BCS. The reaction curve is composed of a component that increases immediately after the plating solution injection and a component that slowly increases over several tens of min. These components suggest that there are multiple holding structures of Cu(I) in the plating solution. Characteristics of the plating solution involved in Cu(I) can be evaluated by analyzing the reaction curve. Assuming that the reaction of Cu(I) with BCS is a first order reaction with respect to the Cu(I) concentration, we obtained the following reaction kinetics of the absorbance, At:</p>
<p class="jove_content" fo:keep-together.within-page="1">At = A0 + AL [1 &#8211; exp (&#8722;t/TL)]</p>
<p class="jove_content" fo:keep-together.within-page="1">t is the time from the start of measurement, A0 corresponds to a component that reacts instantaneously (absorbance at t = 0) and AL corresponds to a component that reacts slowly (At - A0). TL is the time constant of the AL component. To simulate the color reaction curve, we applied the formula to the original analysis software (software may be commercially available)<sup>13,15</sup>. A curve simulating the change in the absorbance of the color reaction of the electroplating solution is shown in <strong class="xfig">Figure 7</strong>. From the simulation, the parameters (A0, AL, TL) related to Cu(I) accumulation are quantified. The simulation results in this figure were A0 = 0.053, AL = 0.098, TL = 13.6 min, and r<sup>2</sup> = 0.998. <strong class="xfig">Figure 8</strong> (graph) plots the simulation value A0 in the plating solution that was electrolyzed for different times. Although the value of A0 did not change greatly until 4 min of electrolysis, an increase corresponding to electrolysis time was seen from 6 min to 10 min.</p>
<p class="jove_content" fo:keep-together.within-page="1">Plating was carried out on a copper substrate for 10 min with the electrolysis solutions to investigate the effect of Cu(I) on the quality of the copper plating such as roughness and morphology. <strong class="xfig">Figure 8</strong> shows the SEM (Scanning Electron Microscope) images of the film surface structure deposited with electrolysis solutions. The film structure at 0 min and at 4 min of electrolysis plating are nearly indistinguishable. There are fine particles adsorbed densely with a size of several tens of nanometers and a smooth surface morphology. After 6 min of electrolysis plating, there is some swelling on the surface. After 10 min of electrolysis plating, there is a large chunky roughness.</p>
<p class="jove_content" fo:keep-together.within-page="1"><img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/59376/59376fig1.jpg" /><br />
<strong>Figure 1:</strong> <strong>Structure and absorption spectrum of Cu (I)-BCS complex. </strong>Fresh copper sulfate plating solution and electrolysis solution. Since Cu(I) is accumulated in the plating solution by electrolysis, the absorption spectrum of Cu(I)-BCS complex is observed in the electrolysis plating solution sample. <a href="https://www.jove.com/files/ftp_upload/59376/59376fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a></p>
<p class="jove_content" fo:keep-together.within-page="1"><img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/59376/59376fig2.jpg" /><br />
<strong>Figure 2:</strong> <strong>Schematic diagram of the equipment for electrification experiment (left) and representative conditions of the electrolysis experiment (right).</strong> <a href="https://www.jove.com/files/ftp_upload/59376/59376fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a></p>
<p class="jove_content" fo:keep-together.within-page="1"><img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/59376/59376fig3.jpg" /><br />
<strong>Figure 3: Picture of a combinations of parts to be energized in the experiment. </strong>Attach the jig with the electrode plate to the glass beaker and connect it to the power supply. (1) Acrylic beaker fixing part, (2) metal electrode parts, (3) copper plate electrode (anode), and (4) platinum plate electrode (cathode). <a href="https://www.jove.com/files/ftp_upload/59376/59376fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a></p>
<p class="jove_content" fo:keep-together.within-page="1"><img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/59376/59376fig4.jpg" /><br />
<strong>Figure 4:</strong> <strong>Absorption measurement of Cu(I).</strong> Absorption measurement procedure (left) and photos of sample solution (right). Fresh copper sulfate plating solution (blue) and electrolysis solution (orange). Since Cu(I) is accumulated in the plating solution by electrolysis, it is colored orange in the electrolysis plating solution sample. <a href="https://www.jove.com/files/ftp_upload/59376/59376fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a></p>
<p class="jove_content" fo:keep-together.within-page="1"><img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/59376/59376fig5.jpg" /><br />
<strong>Figure 5:</strong> <strong>Absorption spectra of Cu(I)-BCS in electrolysis solutions. </strong>Electrolysis time: (<strong>a</strong>) 0, (<strong>b</strong>) 4, (<strong>c</strong>) 6, (<strong>d</strong>) 8, and (<strong>e</strong>) 10 min. Since the absorbance of Cu(I)-BCS generally increases as the electrolysis time becomes longer, it is considered that the amount of Cu(I) accumulated in the plating solution is increased. This figure is a modification of Figure 2 of Koga et al. 2018<sup>15</sup>. <a href="https://www.jove.com/files/ftp_upload/59376/59376fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a></p>
<p class="jove_content" fo:keep-together.within-page="1"><img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/59376/59376fig6.jpg" /><br />
<strong>Figure 6:</strong> <strong>Injection measurement. </strong>Left: Picture of chamber cover. There is a syringe port at the top of the cell; insert a pipette there and inject sample solution. Right: Reaction curve of plating solution which was electrolyzed at 1.0 A for 10 min. A sharp increase in absorbance immediately after injection and a gentle increase are clearly observed. <a href="https://www.jove.com/files/ftp_upload/59376/59376fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a></p>
<p class="jove_content" fo:keep-together.within-page="1"><img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/59376/59376fig7.jpg" /><br />
<strong>Figure 7:</strong> <strong>Simulation of absorbance of plating solution (1.0 A, 10 min).</strong> <img alt="Equation" src="/files/ftp_upload/59376/59376eq1.jpg" />: measured point, solid line: fitting curve. This figure is a modification of Figure 4 of Koga et al. 2018<sup>15</sup>. <a href="https://www.jove.com/files/ftp_upload/59376/59376fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a></p>
<p class="jove_content" fo:keep-together.within-page="1"><img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/59376/59376fig8.jpg" /><br />
<strong>Figure 8:</strong> <strong>Deposition versus electrolysis time. </strong>(Graph) Normalized absorbance fitting parameters are plotted against electrolysis time, A0. (Pictures) SEM images of the plating film surface that were deposited in each electrolysis solution (times above pictures are electrolysis times). <a href="https://www.jove.com/files/ftp_upload/59376/59376fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a></p>

Watch this Scientific Journal Video about Accumulation and Analysis of Cuprous Ions in a Copper Sulfate Plating Solution at JoVE.com

Accumulation and Analysis of Cuprous Ions in a Copper Sulfate Plating Solution

<p class="jove_content">Here, accumulation of cuprous ions in a copper sulfate plating solution in a model experiment and an analysis based on quantitative measurements are described. This experiment reproduces the accumulation process of cuprous ions in the plating bath.</p>

Knowledge of the behavior of cuprous ions (monovalent copper ion: Cu(I)) in a copper sulfate plating bath is important for improving the plating process. ...

accumulation-analysis-cuprous-ions-copper-sulfate-plating

Research

JoVE Journal

Chemistry

14.9K Views.  National Institute of Advanced Industrial Science and Technology (AIST). Here, accumulation of cuprous ions in a copper sulfate plating solution in a model experiment and an analysis based on quantitative measurements are described. This experiment reproduces the accumulation process of cuprous ions in the plating bath.

Video: Accumulation and Analysis of Cuprous Ions in a Copper Sulfate Plating Solution

Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium <em>In Situ</em> Recovery Bleed Water and Its Effect on Cell Viability

<p class="jove_content"><em>In situ</em> recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted through ion exchange. The resultant production bleed water (PBW) contains contaminants such as arsenic and other heavy metals. Samples of PBW from an active ISR uranium facility were treated with cupric oxide nanoparticles (CuO-NPs). CuO-NP treatment of PBW reduced priority contaminants, including arsenic, selenium, uranium, and vanadium. Untreated and CuO-NP treated PBW was used as the liquid component of the cell growth media and changes in viability were determined by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in human embryonic kidney (HEK 293) and human hepatocellular carcinoma (Hep G2) cells. CuO-NP treatment was associated with improved HEK and HEP cell viability. Limitations of this method include dilution of the PBW by growth media components and during osmolality adjustment as well as necessary pH adjustment. This method is limited in its wider context due to dilution effects and changes in the pH of the PBW which is traditionally slightly acidic&#160;however; this method could have a broader use assessing CuO-NP treatment in more neutral waters.</p>

Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium In Situ Recovery Bleed Water and Its Effect on Cell Viability

<p class='jove_content'>Production bleed water (PBW) was treated with cupric oxide nanoparticles (CuO-NPs) and cellular toxicity was assessed in cultured human cells. The goal of this protocol was to integrate the native environmental sample into a cell culture format assessing the changes in toxicity due to CuO-NP treatment.</p>

In situ recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted ...

Environment

ACT1-CUP1 Assays Determine the Substrate-Specific Sensitivities of Spliceosomal Mutants in Budding Yeast

<p class="jove_content">Mutations introduced in the spliceosome or its substrate have significantly contributed to our understanding of the intricacies of spliceosomal function. Whether disease-related or functionally selected, many of these mutations have been studied using growth assays in the model organism <em>Saccharomyces cerevisiae</em> (yeast). The splicing-specific copper growth assay, or ACT1-CUP1 assay, provides a comprehensive analysis of mutation at the phenotypic level. The ACT1-CUP1 assay utilizes reporters that confer copper tolerance when correctly spliced. Thus, in the presence of copper, changes in yeast viability correlate to changes in mRNA production through splicing. In a typical experiment, the yeast spliceosome is challenged with different non-consensus splicing reporters and the splicing factor mutation of interest to detect any synergetic or antithetical impact on splicing. Here a full description of copper plate preparation, plating of yeast cells, and data evaluation are given. A selection of complimentary experiments is described, highlighting the versatility of the ACT1-CUP1 reporters. The ACT1-CUP1 assay is a handy tool in the splicing toolbox thanks to the direct read-out of mutational effect(s) and the comparative possibilities from the continuing use in the field.</p>

<p class="jove_content">The ACT1-CUP1 assay, a copper growth assay, provides a quick readout of precursor messenger RNA (pre-mRNA) splicing and the impact mutant splicing factors have on spliceosomal function. This study provides a protocol and highlights the customization possible to address the splicing question of interest.</p>

Mutations introduced in the spliceosome or its substrate have significantly contributed to our understanding of the intricacies of spliceosomal function. ...

Genetics

Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides

<p class="jove_content">Electrospray ionization (ESI) can transfer an aqueous-phase peptide or peptide complex to the gas-phase while conserving its mass, overall charge, metal-binding interactions, and conformational shape. Coupling ESI with ion mobility-mass spectrometry (IM-MS) provides an instrumental technique that allows for simultaneous measurement of a peptide&#8217;s mass-to-charge (m/z) and collision cross section (CCS) that relate to its stoichiometry, protonation state, and conformational shape. The overall charge of a peptide complex is controlled by the protonation of 1) the peptide&#8217;s acidic and basic sites and 2) the oxidation state of the metal ion(s). Therefore, the overall charge state of a complex is a function of the pH of the solution that affects the peptides metal ion binding affinity. For ESI-IM-MS analyses, peptide and metal ions solutions are prepared from aqueous-only solutions, with the pH adjusted with dilute aqueous acetic acid or ammonium hydroxide. This allows for pH dependence and metal ion selectivity to be determined for a specific peptide. Furthermore, the m/z and CCS of a peptide complex can be used with B3LYP/LanL2DZ molecular modeling to discern binding sites of the metal ion coordination and tertiary structure of the complex. The results show how ESI-IM-MS can characterize the selective chelating performance of a set of alternative methanobactin peptides and compare them to the copper-binding peptide methanobactin.</p>

<p class="jove_content">Ion mobility-mass spectrometry and molecular modeling techniques can characterize the selective metal chelating performance of designed metal-binding peptides and the copper-binding peptide methanobactin. Developing new classes of metal chelating peptides will help lead to therapeutics for diseases associated with metal ion misbalance.</p>

Electrospray ionization (ESI) can transfer an aqueous-phase peptide or peptide complex to the gas-phase while conserving its mass, overall charge, ...

Preparation of Expanded Chitin Foams and their Use in the Removal of Aqueous Copper

<p class="jove_content">Chitin is an underexploited, naturally abundant, mechanically robust, and chemically resistant biopolymer. These qualities are desirable in an adsorbent, but chitin lacks the necessary specific surface area, and its modification involves specialized techniques and equipment. Herein is described a novel chemical procedure for expanding chitin flakes, derived from shrimp shell waste, into foams with higher surface area. The process relies on the evolution of H<sub>2</sub> gas from the reaction of water with NaH trapped in a chitin gel. The preparation method requires no specialized equipment. Powder X-ray diffraction and N<sub>2</sub>-physisorption indicate that the crystallite size decreases from 6.6 nm to 4.4 nm and the specific surface area increases from 12.6 &#177; 2.1 m<sup>2</sup>/g to 73.9 &#177; 0.2 m<sup>2</sup>/g. However, infrared spectroscopy and thermogravimetric analysis indicate that the process does not change the chemical identity of the chitin. The specific Cu adsorption capacity of the expanded chitin increases in proportion to specific surface area from 13.8 &#177; 2.9 mg/g to 73.1 &#177; 2.0 mg/g. However, the Cu adsorption capacity as a surface density remains relatively constant at an average of 10.1 &#177; 0.8 atom/nm<sup>2</sup>, which again suggests no change in the chemical identity of the chitin. This method offers the means to transform chitin into a higher surface area material without sacrificing its desirable properties. Although the chitin foam is described here as an adsorbent, it can be envisioned as a catalyst support, thermal insulator, and structural material.</p>

<p class="jove_content">This study describes a method to expand chitin into a foam by chemical techniques that require no specialized equipment.</p>

Chitin is an underexploited, naturally abundant, mechanically robust, and chemically resistant biopolymer. These qualities are desirable in an adsorbent, ...

Quantifying Fish Swimming Behavior in Response to Acute Exposure of Aqueous Copper Using Computer Assisted Video and Digital Image Analysis

<p class='jove_content'>Behavioral responses of aquatic organisms to environmental contaminants can be precursors of other effects such as survival, growth, or reproduction.  However, these responses may be subtle, and measurement can be challenging.  Using juvenile white sturgeon  (<em>Acipenser transmontanus</em>) with copper exposures, this paper illustrates techniques used for quantifying behavioral responses using computer assisted video and digital image analysis.   In previous studies severe impairments in swimming behavior were observed among early life stage white sturgeon during acute and chronic exposures to copper.  Sturgeon behavior was rapidly impaired and to the extent that survival in the field would be jeopardized, as fish would be swept downstream, or readily captured by predators.  The objectives of this investigation were to illustrate protocols to quantify swimming activity during a series of acute copper exposures to determine time to effect during early lifestage development, and to understand the significance of these responses relative to survival of these vulnerable early lifestage fish.  With mortality being on a time continuum, determining when copper first affects swimming ability helps us to understand the implications for population level effects. The techniques used are readily adaptable to experimental designs with other organisms and stressors.   </p>

<p class="jove_content">Measuring the impacts of environmental contaminants on fish behavior is often subjective and challenging particularly when dealing with sublethal endpoints. We describe methods including video technology to quantify swimming behavior of early life stage white sturgeon (<em>Acipenser transmontanus</em>) during and after 96 hr acute exposures to various concentrations of copper.</p>

Behavioral responses of aquatic organisms to environmental contaminants can be precursors of other effects such as survival, growth, or reproduction.  ...

Neuroscience

A <em>Caenorhabditis elegans</em> Nutritional-status Based Copper Aversion Assay

<p class="jove_content">To ensure survival, organisms must be capable of avoiding unfavorable habitats while ensuring a consistent food source. <em>Caenorhabditis elegans </em>alter their locomotory patterns upon detection of diverse environmental stimuli and can modulate their suite of behavioral responses in response to starvation conditions. Nematodes typically exhibit a decreased aversive response when removed from a food source for over 30 min. Observation of behavioral changes in response to a changing nutritional status can provide insight into the mechanisms that regulate the transition from a well-fed to starved state.</p>
<p class="jove_content">We have developed an assay that measures a nematode&#39;s ability to cross an aversive barrier (<em>i.e.</em> copper) then reach a food source over a prolonged period of time. This protocol builds upon previous work by integrating multiple variables in a manner that allows for continued data collection as the organisms shift towards an increasingly starved condition. Moreover, this assay permits an increased sample size so that larger populations of nematodes can be simultaneously evaluated.</p>
<p class="jove_content">Organisms defective for the ability to detect or respond to copper immediately cross the chemical barrier, while wild type nematodes are initially repelled. As wild type worms are increasingly starved, they begin to cross the barrier and reach the food source. We designed this assay to evaluate a mutant that is incapable of responding to diverse environmental cues, including food sensation or detection of aversive chemicals. When evaluated via this protocol, the defective organisms immediately crossed the barrier, but were also incapable of detecting a food source. Hence, these mutants repeatedly cross the chemical barrier despite temporarily reaching a food source. This assay can straightforwardly test populations of worms to evaluate potential pathway defects related to aversion and starvation.</p>

A Caenorhabditis elegans Nutritional-status Based Copper Aversion Assay

<p class="jove_content">Here, we present a <em>Caenorhabditis elegans</em>-specific assay designed to evaluate changes in copper aversion behavior and the ability to locate a common food source, as the organism progresses from a well-fed to starved nutritional state.</p>

To ensure survival, organisms must be capable of avoiding unfavorable habitats while ensuring a consistent food source. Caenorhabditis elegans alter their ...

Determining the Empirical Formula

<p class="jove_content">Source: Laboratory of Dr. Neal Abrams - SUNY College of Environmental Science and Forestry</p>
<p class="jove_content">Determining the chemical formula of a compound is at the heart of what chemists do in the laboratory every day. Many tools are available to aid in this determination, but one of the simplest (and most accurate) is the determination of the empirical formula. Why is this useful? Because of the law of conservation of mass, any reaction can be followed gravimetrically, or by change in mass. The empirical formula provides the smallest whole-number ratio among elements (or compounds) within a molecular compound. In this experiment, gravimetric analysis will be used to determine the empirical formula of copper chloride hydrate, Cu<sub>x</sub>Cl<sub>y</sub>&#183;nH<sub>2</sub>O.</p>

Determining the Empirical Formula from the Masses of Elements

Source: Laboratory of Dr. Neal Abrams - SUNY College of Environmental Science and Forestry
Determining the chemical formula of a compound is at the heart ...

Education

JoVE Science Education

General Chemistry

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>
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				</tr>
				<tr>
					<td style="text-align: center;">5 min</td>
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					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">1<sup>st</sup> 30 min</td>
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					<td></td>
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				</tr>
				<tr>
					<td style="text-align: center;">2<sup>nd</sup> 30 min</td>
					<td></td>
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					<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

Ogniwa elektrolityczne

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

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

JoVE Lab Manual

Lab Manual Sub Articles

Redox Reactions

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Making Solid Copper<button class="expand">Expand</button>
	<p>In the first half of this lab, you will make solid copper. In this reaction, the solid copper is first oxidized by the strong oxidizing agent, nitric acid, to form water and the salt copper nitrate. The copper nitrate quickly dissociates into the ions, copper(2+) and nitrate, in water. The nitrate anions are reduced to NO<sub>2</sub> gas, which is confirmed by the presence of reddish-brown fumes. The presence of copper ions is indicated by a greenish-blue tint. Adding a base to the mixture changes the color to blue as the copper(II) hydroxide precipitate is formed. The copper(II) hydroxide is relatively unstable; thus, when heat is introduced, a decomposition reaction occurs. In this reaction, water is removed to produce copper oxide, which appears as a black precipitate.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-2">
		<div class="lab-step">Before starting the experiment, put on personal protective equipment, including a lab coat, gloves, and chemical splash goggles.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Weigh between 0.45 and 0.55 g of copper shot and record the exact mass. This experiment must be conducted in the hood, so bring the copper shot back to your workstation.
		<h4><strong>Table 1. Determining percent yield</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always" width="100%">
			<tbody>
				<tr>
					<td>Mass<sub>Cu initial </sub>(g)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Mass<sub>Cu final</sub> (g)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Percent yield</td>
					<td style="text-align: center;"></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/43/Table 1_Determining Percent Yield.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Label a 10-mL graduated cylinder as &#8216;8 M nitric acid&#8217; and measure 8 mL of the solution provided by your instructor. Cover the cylinder with a watch glass when transporting the solution back to your hood.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">To begin the experiment, place the copper in a 50-mL beaker.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Slowly add the 8 mL of 8 M nitric acid while stirring with a stirring rod. <strong>Note:</strong> If the copper does not fully dissolve, place the beaker on a hotplate set to 30 &#176;C for approximately 2 min, while continually stirring. Here, the solid copper is reacting with the nitric acid to form copper nitrate, water, and NO<sub>2</sub> gas. Do not overheat the solution or the nitric acid will boil off.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Once the copper is fully dissolved, remove the beaker from the hotplate and set the temperature on the hotplate to 85 &#176;C.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Measure 150 mL of deionized water using a 50-mL graduated cylinder and transfer the water into a 400-mL beaker.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Slowly, and while stirring, pour the copper solution into the 400-mL beaker containing water.<br />
		<strong>Note:</strong> If there is copper solution left in the beaker, use a pipette to rinse the rest of the solution into the larger beaker.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Label a 50-mL graduated cylinder with &#39;3 M NaOH&#8217; and obtain 20 - 30 mL of 3 M NaOH from your instructor. Cover the graduated cylinder with a watch glass while carefully carrying it back to your hood.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Add 10 mL of the NaOH to the 400-mL beaker while stirring.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Test the pH of the solution using pH paper. Continue adding NaOH until the solution is basic or about pH 10. Here, the copper nitrate reacts with NaOH to form the blue precipitate, copper(II) hydroxide, and sodium nitrate.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Place the 400-mL beaker on the hotplate and use a glass thermometer to monitor the temperature. Once the solution reaches 85 &#176;C, let it remain there for 10 min. Stir slowly with the stirring rod, as this will evenly distribute heat while not disrupting crystal formation.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">After 10 min, turn off the hotplate and remove the beaker. Allow the beaker to cool to room temperature. As the solution cools, a dark precipitate will appear at the bottom of the beaker, while a clear and colorless liquid, the supernatant, will separate towards the top. The crystals are the copper oxide.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Once the solution has cooled completely, label a new beaker as &#39;aqueous waste&#39;, and remove the supernatant by carefully pouring it into the waste container. Try not to lose the precipitate at the bottom of the beaker.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Set up the filtration system by attaching the silicone tubing between the house vacuum and the vacuum flask. Place a B&#252;chner funnel into the vacuum flask using a rubber adapter. Now, place one filter paper in the B&#252;chner funnel and wet it with deionized water.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Turn on the vacuum. Pour the precipitate into the B&#252;chner funnel and direct it into the center with the stirring rod. Use deionized water to rinse all the precipitate into the funnel. When all the precipitate is out of the beaker, turn off the vacuum.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Remove the filter paper with the precipitate and place it into the beaker. The dark precipitant on the filter paper is the copper oxide, which should be left to dry for a day or two before it is used in the next reaction.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Clean up from the experiment. First, empty the liquid in the filter flask into the aqueous waste beaker. Then, test the aqueous waste with pH paper. <strong>Note: </strong>Any waste that is higher than pH 10 should be neutralized with citric acid. Any waste below pH 4 should be neutralized with baking soda.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Neutralize the unused NaOH with citric acid and then pour it down the drain with copious amounts of water. Anything containing black particles indicates the presence of copper oxide and should be disposed of in the heavy metal drum container.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Making Copper Oxide<button class="expand">Expand</button>
	<p>The copper oxide produced in the previous lab section is insoluble in water but can be dissolved in sulfuric acid. When this occurs, the copper(2+) cations and the sulfate anions are reintroduced through a double displacement reaction. When zinc is added in the final step, the copper(2+) ions are reduced to solid copper through a single displacement reaction.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-2">
		<div class="lab-step">Put on the appropriate protective equipment, such as a lab coat, gloves, and chemical splash goggles.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Obtain the dried copper oxide that was prepared in the last lab exercise and remove as much copper oxide from the filter paper as possible using a rubber policeman. Place the solid and filter paper back into the same 400-mL beaker it was stored in.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Label a 10-mL graduated cylinder as &#39;5.93 M sulfuric acid&#39; and obtain 8 mL of sulfuric acid from the instructor. Cover the graduated cylinder with a watch glass, and carefully carry the sulfuric acid to your hood. <strong>Note: </strong>Perform the next step of the experiment in the hood.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Use a plastic pipette to add about 5 mL of sulfuric acid directly onto the filter paper in the beaker.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Then, hold the filter paper with tweezers and use a metal spatula to scrape off as much solid as possible without ripping the filter paper. Use as little sulfuric acid as possible to rinse the copper oxide, as excess sulfuric acid will require more zinc later.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Rinse copper oxide from the filter paper with 2 mL of deionized water and add a little more deionized water to the beaker. Once the copper oxide has been removed from the filter paper, dispose of the filter paper as solid waste.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Stir the solution until the copper oxide is fully dissolved. If the solid does not dissolve, place the beaker on the hot plate and heat it to about 60 &#176;C.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Add 3 - 5 mL of water and stir to dissolve. Be careful not to go higher than this temperature, as the liquid could evaporate leaving a precipitate of copper sulfate.</div>
		</li>
		<li data-sub-note-item="2-10">
		<div class="lab-step">Weigh 1.2 g of zinc and record the exact mass in your lab notebook.</div>
		</li>
		<li data-sub-note-item="2-11">
		<div class="lab-step">Slowly add half of the zinc to the solution. Crush and stir the zinc using the stirring rod to fully dissolve all particles. The solution should be colorless. If color is still present, add more zinc until the color disappears.</div>
		</li>
		<li data-sub-note-item="2-12">
		<div class="lab-step">Once the color fully disappears, weigh the remaining zinc in the weigh pan, and subtract it from the original mass to obtain the mass of the zinc used. Here, the zinc has reacted with the copper sulfate to form zinc sulfate and solid copper.</div>
		</li>
		<li data-sub-note-item="2-13">
		<div class="lab-step">Decant the supernatant from your solution into the container labeled &#39;aqueous waste&#39;. Then, preheat the hot plate to 40 &#176;C. Obtain 10 mL of 6 M hydrochloric acid from your instructor in a labeled graduated cylinder. Cover the opening of the cylinder with a watch glass and bring the acid back to your hood.</div>
		</li>
		<li data-sub-note-item="2-14">
		<div class="lab-step">Add 5 mL of the hydrochloric acid to the remaining precipitate to dissolve any zinc present within the solid copper.</div>
		</li>
		<li data-sub-note-item="2-15">
		<div class="lab-step">Place the beaker on the preheated hot plate and warm the solution for 2 min. The bubbling observed here is the neutralization reaction taking place to dissolve the zinc. Make sure that the reaction does not boil. Then, turn the heat setting on the hot plate off.</div>
		</li>
		<li data-sub-note-item="2-16">
		<div class="lab-step">Once the bubbling subsides, add 2 - 3 mL of additional hydrochloric acid. Continue adding acid in 1-mL increments until the bubbling completely stops.</div>
		</li>
		<li data-sub-note-item="2-17">
		<div class="lab-step">Decant the supernatant, wash the precipitate with 5 - 10 mL of water, and decant any remaining supernatant. <strong>Note: </strong>If the copper particles are too small to decant the liquid without losing them, set up a B&#252;chner funnel apparatus with filter paper and no vacuum. Pour the solution through the funnel so the particles are retained on the filter paper, then return the particles to the beaker. Repeat the wash and decant steps two more times.</div>
		</li>
		<li data-sub-note-item="2-18">
		<div class="lab-step">Replace the filter paper in the B&#252;chner funnel with a fresh one and wet it slightly with water. Then, turn on the vacuum for a moment to help the filter settle into place.</div>
		</li>
		<li data-sub-note-item="2-19">
		<div class="lab-step">Add approximately 5 mL of water to the copper precipitate, and then pour it into the funnel in the center of the filter paper. Stir the copper gently to remove the impurities while taking care not to rip the filter paper.</div>
		</li>
		<li data-sub-note-item="2-20">
		<div class="lab-step">Turn the vacuum on, and let it run for 2 min.</div>
		</li>
		<li data-sub-note-item="2-21">
		<div class="lab-step">Close the vacuum and disconnect the tubing from the flask. Remove the funnel and dispose of the liquid in the aqueous waste container.</div>
		</li>
		<li data-sub-note-item="2-22">
		<div class="lab-step">Reconnect the B&#252;chner funnel setup and reattach the vacuum tubing.</div>
		</li>
		<li data-sub-note-item="2-23">
		<div class="lab-step">Obtain about 10 mL of methanol and pour 3 mL onto the copper in the funnel. Then, turn on the vacuum and let the copper dry for 2 min.</div>
		</li>
		<li data-sub-note-item="2-24">
		<div class="lab-step">Dry the precipitate with methanol two more times, running the vacuum after each wash. During the last drying phase, place a large rubber stopper on the B&#252;chner funnel, and let the vacuum run for 5 min. Then, close the vacuum and disconnect the vacuum tube.</div>
		</li>
		<li data-sub-note-item="2-25">
		<div class="lab-step">Remove the large stopper and let the copper air dry for 30 min.</div>
		</li>
		<li data-sub-note-item="2-26">
		<div class="lab-step">Label an empty beaker as &#39;organic waste&#39; and pour the liquid from the filter flask into the organic waste container.</div>
		</li>
		<li data-sub-note-item="2-27">
		<div class="lab-step">Tare an empty weighing pan and transfer as much of the copper as possible from the filter paper to it. Weigh the copper and record its mass.</div>
		</li>
		<li data-sub-note-item="2-28">
		<div class="lab-step">Clean up from the lab exercise. Dispose of the organic waste and excess methanol in the organic waste container. Test the aqueous waste with pH paper and neutralize it with either citric acid for highly basic pH or baking soda for acidic pH.</div>
		</li>
		<li data-sub-note-item="2-29">
		<div class="lab-step">Dispose of the supernatant liquid in the heavy metal drum waste container because it contains zinc. The unused sulfuric acid and hydrochloric acid should be neutralized with baking soda and then washed with plenty of water down the sink.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="3" data-parent-collapse="">Results<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="3-1">
		<div class="lab-step">Determine if the product is pure. Spread some of the product on an indicating desiccant to test for the presence of methanol. The desiccant will change from blue to turquoise if methanol is present.</div>
		</li>
		<li data-sub-note-item="3-2">
		<div class="lab-step">Drop a few drops of 6 M HCl onto the product to see if it will react with any NaOH that may be left over. If NaOH is present, you will see bubbling.</div>
		</li>
		<li data-sub-note-item="3-3">
		<div class="lab-step">If the product is copper, it should look like dark-red granules. If the product is black, you have failed to make copper and instead made copper oxide.</div>
		</li>
		<li data-sub-note-item="3-4">
		<div class="lab-step">Calculate the percent yield using the initial and final mass of copper. The percent yield is the ratio of the actual yield, in this case, the final mass of copper, to the theoretical yield, or the initial mass of the copper, multiplied by 100. It is impossible to obtain a percent yield greater than 100. If this occurs, there was an error in calculation &#8212; or the product was still wet &#8212; which added more weight.</div>
		</li>
	</ul>
	</li>
</ol>

Redox Reaction: Oxidation States - Procedure

Reakcje redoks

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

	Making Solid CopperExpand
	In the first half of this lab, you will make solid copper. In this ...

Precipitation and Co-precipitation

<p>Precipitation and coprecipitation methods can be used to separate a mixture of ions in a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent are separated based on the differences in solubility products. For example, consider the separation of Cu(II) and Fe(II) ions by precipitation as insoluble sulfides. First, copper(II) sulfide is precipitated by the addition of acidic H<sub>2</sub>S, where the dissociation of H<sub>2</sub>S is suppressed. Adding H<sub>2</sub>S increases the product of sulfide ion and copper ion concentrations. When this product exceeds the solubility product of copper(II) sulfide, precipitation occurs. On the other hand, H<sub>2</sub>S alone cannot be used to precipitate iron(II) sulfide because its solubility product is higher than that of copper(II) sulfide. Successful precipitation of FeS requires the addition of aqueous ammonia.</p>
<p>Coprecipitation is a method used to remove otherwise soluble contaminants by using a substance that can coprecipitate with the contaminants. This technique can be used to isolate trace components from a solution. For instance, the tendency of arsenic to coprecipitate with ferric hydroxide is exploited in a process called gathering. During this process,&#160; Fe(II) or solid iron particles are added to water contaminated by arsenic. The iron particles are then oxidized for several hours to obtain ferric hydroxide precipitates, which now contain arsenic. Finally, the arsenic-bearing precipitate is removed by repetitive filtration to produce safe drinking water.</p>

Opady atmosferyczne i współopady

Precipitation and coprecipitation techniques can be applied to separate a mixture of ions.
When different ions form sparingly soluble salts with the same ...