inspector071
Member
- Joined
- Sep 29, 2013
- Messages
- 21
I have a little over 700g of a roughly 80/20 Ag/Cu alloy that I'm trying to recover the silver from. The alloy seems to have been part of a little metallurgy experiment, as much of the metal was inside quartz test tubes and quartz crucibles. The tubes were labeled with the corresponding alloy, so I'm assuming copper and silver are the only two metals present. In a 2L beaker I added the metal to roughly a liter of 2:1 70% nitric acid to distilled water. The reaction commenced, forming plenty of nitrogen dioxide. Unfortunately, I let it get a little too hot and a little of it boiled over. As the reaction calmed down, the solution began to turn opaque white, forming a dense and thick precipitate that settled slowly. The precipitate would best be described as a sludge. It is unfilterable with Whatman GF/C and hardened 50 filters. After settling for a week, the precipitate fills up about half of the 2 L beaker. I had expected this to be an easy process: dissolve the silver and copper, be left with a clear blue solution, then cement out the silver with copper. I siphoned off some of the clear, light blue solution after letting it settle and attempted to cement out any of the silver using copper. Indeed, the solution contains silver nitrate as silver cements out, however, there seems to be excess acid as the silver redissolves as soon as I remove the copper. I took a sample of the sludge and attempted to dissolve it in hot distilled water. It did not seem to dissolve at all. While all of this sounds similar to silver chloride, no source of chloride has been used anywhere near this. And certainly not enough chloride to produce this much silver chloride. Any thoughts on what this sludge is and why it formed? Also, what is the best way to remove excess nitric acid from a silver nitrate solution?