![]() However, I've never had a need to use HCl/bleach, so I may be talking through my hat. Just add the sodium sulfite or SMB, pretty much as I've outlined above, and test often with stannous chloride. If you used HCl/bleach to dissolve the foils, there is no nitric to worry about. For a noobie, boiling down the aqua regia is the most guaranteed method. You must effectively get most of the nitric out - whether using urea, boiling down, or using my minimum nitric method - before using sodium sulfite or SMB, or you can have problems. I probably ended up cementing the gold on copper and starting over. One time, when I was a noobie, I remember adding pounds of sodium sulfite and still couldn't get the gold to drop. A little nitric can consume a lot of sodium sulfite. If you have free nitric left, it will take more. I would dissolve about that much in a minimum amount of hot water, add some of it, stir well, and test with stannous chloride. If there is no free nitric left in the solution, it will take about the same weight of sodium sulfite as you have gold, or a little more. I also seem to remember that a copper compound can precipitate. This can be removed in the filter with hot water. I know that, with a great excess, some will sit on the bottom, undissolved, and will get mixed with the gold powder. Since I haven't added too much sodium sulfite for many years, I can't exactly remember what happened. You should always use stannous chloride to prove any of the sensory guides that I spoke of. If gold is still in the solution after adding some sodium sulfite and stirring well, you probably won't smell SO2. The smell of SO2 is only a guide that I use. I bought it in 50# bags, but you used to be able to buy Kodak Photo grade, in 1# packages, from camera stores that sell film processing chemicals (if they still exist). I liked Photo grade because it is fairly pure, yet not too expensive. I think I used Stauffer brand Photo Grade sodium sulfite. By the way, how serious are the consequences for adding excess SS (or any other reducing)? Unfortunately I don't have this, reason why I wouldn't want to add more than it is necessary. for GSP one of the signs of a succesfull precipitating is the smell of sulfur, but this is possible only by having a long practice. I know that those with experience guide themselves after data/signs, eg. Which would be the SS ration for the AR solution that contains 8 gr foils (estimated 7 gr gold), does the water need to be warmed up? I got today this sodium sulfite, here are it's characteristics: My Berzelius with the AR stays uncovered of two days. A part of them dissolved slowly, the others remained intact, this made me think, that "excess nitric" is ok. It contains 8 gr foils, the nitric necessary in dissolving these was added in small amounts (until it was completely dissolved), I even tried to use Harold's trick, only that instead of the button I used a few foils. I have a sample of 150 ml clear yellow AR (diluted 1x3 water, filtrated ). I believe that I’ve reached the precipitating stage.
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