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Marshall, You are right that the amount of citric acid is high but I think it is not as high as you indicate. As you noted before, you can only achieve about a 285 ppm concentration of silver citrate in water. To get higher concentrations, you need to have the silver citrate dissolved in a citric acid solution and that is the reason for the additional citric acid. In my first attempt at silver citrate, I used a 10 percent solution because the following patent performed testing with solutions of 1, 5, and 10 percent: http://www.freepatentsonline.com/6197814.html. According to the patent, 400 ppm SC made with 5 and 20 percent solutions of citric acid are stable during storage but with 1 percent it was not. I had plenty of citric acid powder so I went with 10 percent for the first try. Next, I used a 5% solution, by volume, of citric acid dissolved in distilled water for concentrations of up to 600 ppm. Measurement of the citric acid was not critical since I used more citric acid than is necessary. Currently, I am using 1/8 cup for 2 liters water, which I think is in the 2 - 3% range. I do it to keep the tart taste of the SC at an acceptable level while easing the effort to make the SC. The solution is stable over time too. I use a manual setup with no stirring. When I make the SC, I just cut the top off a gallon distilled water plastic bottle to where I will have 2 liters water in the container and a little additional height to prevent spillage. The separation if the electrodes is determined by the container's width..Given, the conductivity of the solution, I could use a wider container but there is no need to. My earlier attempts with higher citric acid concentrations showed a little formation of silver oxide on the negative electrode near the end if the generation. With the current concentration I see oxide formation starting just around the 200 ppm concentration. So I continue to use the 1/8 cup of citric acid to minimize the need to clean the electrode. Also, the higher citric acid concentrations showed little or no current drop off during the generation. At the present concentration, I do see some drop off of electrode current. The current plus the silver oxide formation indicate to me that I might be getting around the max ppm for the concentration. Remember that the patent indicated that 400 ppm at a 1% solution is not stable and that some of the citric acid is consumed in the making of the silver citrate. Just FYI: If you use enough citric acid you can generate silver citrate solutions to over 23,000 ppm. See Figure 4 in: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2590638/: "Silver citrate is a white substance with a very limited solubility in water. Under the normal physicochemical conditions, 1 part of silver citrate is soluble in 3500 parts of water, which corresponds to 285 ppm of Ag(I) ion in the solution [11]." "Formation of silver citrate/citric acid complexed solutions was investigated. Although, silver citrate is minimally soluble in water, it can successfully be dissolved in citric acid solutions. The maximum concentration of Ag(I) in solution is estimated at 23 to 25 g/L if the concentration of citric acid is at least 4 mol/L or higher." In the report above, the graph in Figure 4 shows how much citric acid you need vs the ppm of the silver citrate. Please note that the graph does not include the citric acid needed to create the silver citrate in the first place so one will need to use more than is shown. Regards, Steve N -----Original Message----- From: Marshall Dudley [mailto:mdud...@king-cart.com] Sent: Monday, November 30, 2009 10:27 AM To: silver-list@eskimo.com Subject: Re: CS>Use of high ppm CS That seems excessive for the citric acid. That would produce over 2000 ppm silver citrate if you ran it to completion. Marshall Norton, Steve wrote: > > You need to use powdered citric acid. I use 1/8 cup for 2 liters > water. The citric acid increases the conductivity of the solution so > you cannot use an automated CS generator. Also if the generator uses > current limiting it will take a long time to get to a high ppm. A > manual setup without current limiting is best. Also, a battery powered > setup may not have enough current capability. > - Steve N >
