I have recently refined a batch of silver powder by dissolving 300 grams of sterling silver chains in nitric acid
adding sodium chloride to precipitate silver chloride
adding sodium hydroxide to convert the silver chloride to silver oxide
adding sugar to reduce the silver oxide back to silver metal
washing with hydrochloric acid to remove copper and nickel hydroxides
vacuum filtering and washing with copious amounts of water
and then oven drying the precipitate
After oven drying the silver powder for 4 hours at 500 degrees I was left with lumps of what seemed to be dry silver but the weight came out to 325 grams which I found very odd considering there was 300 grams of metal initially and there should only have been 277 grams of silver metal. I just assumed there must have been a bunch of water trapped in the silver that was struggling to boil off due to the extremely small particle size of the powder that made up the huge lumps of silver after it was oven dried.
Today I attempted to redissolve the silver lumps with nitric acid to make silver nitrate. I used an excess of azeotropic nitric acid that I believed to be contaminated with a small but still significant amount of ammonium nitrate. Very little silver would go into solution so I decided to filter off the acid and rinse the remaining silver powder and start again. I now put the silver powder into a beaker with some very pure nitric acid with about an 85% concentration but even after hours of refluxing the powder in the acid it a large amount of silver remains.
Help!?
adding sodium chloride to precipitate silver chloride
adding sodium hydroxide to convert the silver chloride to silver oxide
adding sugar to reduce the silver oxide back to silver metal
washing with hydrochloric acid to remove copper and nickel hydroxides
vacuum filtering and washing with copious amounts of water
and then oven drying the precipitate
After oven drying the silver powder for 4 hours at 500 degrees I was left with lumps of what seemed to be dry silver but the weight came out to 325 grams which I found very odd considering there was 300 grams of metal initially and there should only have been 277 grams of silver metal. I just assumed there must have been a bunch of water trapped in the silver that was struggling to boil off due to the extremely small particle size of the powder that made up the huge lumps of silver after it was oven dried.
Today I attempted to redissolve the silver lumps with nitric acid to make silver nitrate. I used an excess of azeotropic nitric acid that I believed to be contaminated with a small but still significant amount of ammonium nitrate. Very little silver would go into solution so I decided to filter off the acid and rinse the remaining silver powder and start again. I now put the silver powder into a beaker with some very pure nitric acid with about an 85% concentration but even after hours of refluxing the powder in the acid it a large amount of silver remains.
Help!?