To List; Here is the promised report.
Making Ions Visible ~~~~~~~~~~~~~~~~~~~ The purpose of this experiment is to visualize the flow of ions in the cs process. A pH indicator is added to the distilled water, and silver and hydroxyl ions are detected by changes in color. Although the pH indicator modifies the process, we can view some of the dynamics of the cs process as they occur. pH Indicators ~~~~~~~~~~~~~ Phenolphthalein is expensive and a potential carcinogen. It was used as an ingredient in laxatives such as Ex-Lax and could easily be extracted with alcohol. It was removed by order of the FDA in 1977: http://www.fda.gov/bbs/topics/NEWS/NEW00589.html Another simple pH indicator can be made from the anthocyanin in red cabbage. There is no doubt it affects the cs process, but enough of the process remains intact to be able to make useful observations. Extracting Anthocyanin From Red Cabbage ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Cut the leaves of a red cabbage into pieces and fill a 1/2 litre glass about 3/4 full. Cover with distilled water and bring to a boil in a microwave oven. Run at low heat for 30 minutes and let cool. The purple liquid is what we are after. It is not very accurate as a pH indicator, but it can be quite useful over a wide pH range. It may keep up to several weeks in the refrigerator if kept in a closed container. Pour some liquid on a paper napkin. A drop of vinegar will turn pink, and bleach should turn yellow. You can soak a coffee filter with the solution and let dry, then cut into strips for later use. Here is a typical color chart: pH Color 2 Red 4 Purple 6 Violet 8 Blue 10 Blue-Green 12 Greenish Yellow Here is an interesting demo showing the color obtained from various household products: http://www.cchem.berkeley.edu/demolab/demo_txt/CabbIndic.htm Here is another showing the colors obtained with a pH of 1 to 12: http://www.rhodium.ws/chemistry/equipment/ph-indicator.html Here is a demo of the colors obtained with lemon juice and household detergent: http://www.mr-damon.com/experiments/6svt/ph_cabbage.htm Anthocyanin and CS ~~~~~~~~~~~~~~~~~~ The colors obtained in the cs process are not mentioned in any of the above reports. Silver ions show up as a very pale white color, and hydroxyl ions give a deep bronze color. The deep bronze overwhelms the pale white, so it is impossible to tell what happens at the cathode. Even with a very low concentration of anthocyanin, the entire solution turns bronze and hides everything, so the time available for observation is somewhat limited. Other plants contain different pH indicators. It might be possible to find one that is less sensitive to the hydroxyl ion: http://chemengineer.miningco.com/cs/acidsandbases/a/aa060703a.htm It also might be possible to find an indicator that fluoresces under the ultraviolet light from a mercury lamp, where the action is modified by the ions present during the cs process. Electrode Arrangement and Test Setup ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ One electrode consists of 4 straight 12 ga rods in parallel. The other electrode is 12 ga wire formed into a "W". Each electrode has approximately 3.8 square inches of wetted area. The spacing between electrodes can be adjusted by bending the electrodes. It currently averages about 1 1/8 inch. In general, variations in spacing seem to have only a minor effect on the process. What counts is the wetted area for both electrodes, and the shape of the electrode. The "W" electrode definitely gives better performance than the straight rods due to the absence of sharp edges. The current source is a 160V resistive-limited constant current source. It consists of a bank of switched resistors connected to a 120VAC rectifier and filter. The basic circuit is shown below. CAUTION - do not try to build this unless you know how to protect yourself and others from the lethal voltages and currents present. http://www.geocities.com/mrmonett/shingles/120vac.gif Resistor R3 can be any or all of the following values in parallel: 100k, 200k, 400k, 750k, 1.5meg, and 3meg. This allows current settings of 53uA to 3.3mA in steps of 53uA. These values do not form an exact binary sequence, but it is close enough. The current is monitored with a Keithley Model 177 Microvolter. The voltage across the cell is monitored with a HP 34560A digital voltmeter. The current changes slightly with line voltage and cell resistance, but it is more than adequate for the cs process. The high source voltage allows operation over a wide range of cell resistances. The glass is an ordinary 1/2 litre drinking glass with straight sides. The outside diameter is 2.79 inches and the volume to the fill line measures approximately 425 ml. First Experiments ~~~~~~~~~~~~~~~~~ The first experiments were somewhat crude and only served to get a rough idea of what happens when anthocyanin is added to the cs process. The first comment is the cell resistance drops dramatically, which means this experiment should be conducted using a constant current source. If a voltage source is used, a series resistance is needed to limit the current. I used a current setting of 3.3 mA and varied the current density by changing the volume of water. The current density is given in each experiment. A second note is fairly high currents are needed in order to observe the reactions before the entire solution is dominated by the bronze color from hydroxyl ions. This limits the range of current densities that can be studied. A variable voltage or current supply would help immensely by providing the ability to modify the current as needed to examine the process in finer detail. Several interesting observations were obtained as described below. Embarrassingly, I really didn't expect the experiment to work, and when things started happening, I was too fascinated to keep accurate track of the time. Experiment #1 - An Ion Cloud ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Cell current = 3.33 mA, current density = 3.3/3.8 = 0.868 mA/sq.in. The cs generator was filled with dw and enough anthocyanin was added to turn the solution purple. The electrodes were still visible. After turning on the current, the voltage across the cell was about 1 Volt. This shows the cell resistance is lowered dramatically by the pH indicator. The voltage rose slowly for several minutes as various ions collected at their respective electrodes, raising the cell resistance. Then it started to drop, indicating silver ions were being released from the anode. Soon, a faint white cloud appeared around the anode rods. It was very uniform along the length of the rods, had a very distinct edge, and could be seen clearly against the purple background of the dw. The thickness of the cloud was hard to estimate due to the magnifying effect of the round glass. I think it was about 0.030 inches. A vigorous current of unidentified material began falling off the anode rods to the bottom of the glass. It quickly filled the bottom and was too dense to see through. At this time, the cathode area was completely opaque, and a dark cloud filled glass about halfway to the anode. Since this experiment seemed to be done, it was terminated. Experiment #2 - Ions Between Electrodes ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Cell current = 3.33 mA, current density = 3.3/1.9 = 1.736 mA/sq.in. The cs generator was half-filled with dw and enough anthocyanin was added to turn the solution faint purple. After gentle stirring, some wisps remained in the solution. After turning on the current, the cell voltage rose for several minutes, then started falling as before. The solution was now too clear to observe the faint cloud around the anode. After about five minutes, some of the wisps of anthocyanin started showing a reaction. The anode was on the left, and the edges of the anthocyanin facing the anode started turning faint white. Other wisps closer to the cathode started turning a bronze color. Finally, the two reactions met in the middle of the glass, about halfway between the electrodes. Once the anthocyanin changed color, it remained the same color. About this time, I noticed a fairly thick brown stream falling from the bottom of each anode rod. It collected in a thick mist at the bottom of the glass. The area on the cathode side started turning a rich bronze color. I let the experiment continue while I ate supper. When I returned, the entire glass was filled with a very deep, rich wine color and nothing else was visible inside the glass. With nothing else to see, the experiment was terminated. Experiment #3 - Anode Streamers ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Cell current = 3.33 mA, current density = 3.3/1.9 = 1.736 mA/sq.in. The cs generator was filled with dw and a small amount of anthocyanin was added. The solution remained clear. After turning on the current, the cell voltage rose for several minutes, then started falling as before. The voltage was much higher than previously, but I failed to record it. After a period of time, a rich bronze color started appearing around the cathode. Thin brown streamers started falling from each anode rod. Three fell vertically, and one was slightly tilted. Eventually, the entire glass filled with the rich bronze color and the experiment was terminated. Conclusion ~~~~~~~~~~ There are far too many conclusions and further questions to list. Here are some main ones: Introducing the pH indicator at the beginning modifies the process, and the hydroxyl changes the anthocyanin to a deep bronze color which eventually hides everything. It might be possible to insert pH strips at the desired time and place to examine the process with less interference from the pH indicator. Also, there are pH strips that do not bleed into the solution, but they are expensive. A video camera would be helpful to record the process. It may have difficulty picking up the faint white color from the silver ion reaction with anthocyanin. Sometimes it was quite difficult to keep track of things happening simultaneously at different locations. The internal time stamp of a video camera would be extremely helpful in tracking these fast-changing situations. This experiment seems very simple and easy to do. It is also quite tasty. It turns out that cabbage boiled in distilled water is delicious, and it makes a perfect snack while you are waiting for something to happen;) It also seems simple enough that surely someone has tried it before. If anyone knows of a link, please post it. Best Regards, Mike Monett -- The silver-list is a moderated forum for discussion of colloidal silver. Instructions for unsubscribing may be found at: http://silverlist.org To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
