Cool. I think I will try the same experiment with Phenolphthalein. Another good choice might be hydrangia, they are pink in acid and blue in bases.
Marshall Mike Monett wrote: > 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]>
