Side reactions while dissolving silver

[ldanielrosa]

TL;DR

poor man's nitric acid and 'corrosion inhibitors' in drain opener

I have some assorted silver scrap that I committed to refining/recycling. I decided I prefer to save money and avoid bureaucratic headache by making "poor man's nitric acid" with sulfuric acid drain opener and calcium nitrate.

The first stage goes well enough. I use gravity filtration on the mud and run about 25% of the liquid volume of water through it, twice, to scavenge what I reasonably can. The rest goes with the chicken manure and ashes to be used in the garden later.

The product is somewhat less than 8 molar nitric acid, with impurities. I am aware that there will be some dissolved calcium nitrate and possibly a slight excess of sulfuric acid, both of which will generate silver sulfate as a side product. This is not the first item I'm asking about.

After stirring with heat, I allow the liquor to sit still then decant the clear portion into another container. Here I add copper wire to precipitate the silver. There is inconsistency in precipitate color between batches, sometimes grey and sometimes lavender. After washing and drying the precipitate, the conductivity is not good. I have never seen this when using better quality nitric acid. Is the corrosion inhibitor coating the surface and possibly entrapping come of the copper ions?

I am not sure what more to say or ask. Does anybody here have experience with this?

 

[.Scott]

I am hoping that you have consulted an MSDS for the materials you are dealing with. The two concerns I notice are proper PPE (glove, glasses, whatever) and the potential for dealing with hazardous waste. In the US, the setting (your home) and the kind of small quantities you're likely working with would be considered "Household Hazardous Waste" - which is more lightly controlled than regular industrial hazardous. I am hoping that the "garden" you mentioned is not a vegetable garden. You're not going to accidently ingest an LD50's worth of these salts, but there's a certain yuck factor to having veggies with silver. Even if it wouldn't kill you, it could discolor you.