silver refining problem

[joheleh]

hi ,

P could also mean plated.

U could have bought a 1 ounce 9999 silver maple leaf for 18,50 euros this week :roll:

Pat

let's see...

 

[MysticColby]

the melting dish can be cleaned fairly easily by soaking it in dilute nitric acid (~5%) overnight or with a little heating, then rinsed in water, then dried excessively, then very slowly heated before the next melt. melted borax doesn't really dissolve in water, but it does slowly dissolve in acid. nitric will dissolve any silver or copper BB's in the borax, which you can then cement with a copper bar later and add to your next melt.

from the look of that first ingot, I'd say the cemented silver was not washed well enough. It should be washed somewhere around 10 times the volume of cemented silver you have. I usually let the cemented silver settle, decant the copper nitrate, add water, stir, let settle, decant, repeat 3 more times, then pour cemented silver into a filter and rinse with water until absolutely no color remains in the filtrate. If it takes too long, put it back in the settle/decant step.

so the bar was marked 38.88g, but you weighed it to be 39.88g. What did you use to weigh it? digital scales are not exactly reliable, and require calibration with known standards. Mine says the 200g standard I have weighs 199.3g (I'm unable to calibrate it, but I do take this into account when doing calculations). The main reason for this is that gravity on earth is not constant for different areas. I hear some parts of Canada has the lowest gravity. http://science.howstuffworks.com/environmental/earth/geophysics/missing-gravity.htm

 

[joheleh]

thank you very much. i have decided to put it in nitric bath. tomorrow morning i'll check the results.

 

[moose7802]

So before you add the copper bar to cement out the Ag couldn't you add a little sulfamic acid to use up the rest of the free nitric, then cement out Ag?

Tyler

 

[butcher]

Or save it for that next batch of silver.

 

[joheleh]

the melting dish can be cleaned fairly easily by soaking it in dilute nitric acid (~5%) overnight or with a little heating, then rinsed in water, then dried excessively, then very slowly heated before the next melt. melted borax doesn't really dissolve in water, but it does slowly dissolve in acid. nitric will dissolve any silver or copper BB's in the borax, which you can then cement with a copper bar later and add to your next melt.

from the look of that first ingot, I'd say the cemented silver was not washed well enough. It should be washed somewhere around 10 times the volume of cemented silver you have. I usually let the cemented silver settle, decant the copper nitrate, add water, stir, let settle, decant, repeat 3 more times, then pour cemented silver into a filter and rinse with water until absolutely no color remains in the filtrate. If it takes too long, put it back in the settle/decant step.

so the bar was marked 38.88g, but you weighed it to be 39.88g. What did you use to weigh it? digital scales are not exactly reliable, and require calibration with known standards. Mine says the 200g standard I have weighs 199.3g (I'm unable to calibrate it, but I do take this into account when doing calculations). The main reason for this is that gravity on earth is not constant for different areas. I hear some parts of Canada has the lowest gravity. http://science.howstuffworks.com/environmental/earth/geophysics/missing-gravity.htm

here it is the crucible after 14 hours of soaking, i think i'll leave it here for another day, seems to work great.


and here my washed( 10 times with water and 3 times with boling distilled water...every time stirred and let it settle), dried silver powder, ready for melting. those are 69.1g

 

[MysticColby]

the cemented silver will always look shiny and pure. it's the supernatant or filtrate that needs to be free of all color.
(supernatant = liquid above the settled silver, filtrate = liquid that passes through the filter)
Any color in either of these will likely be copper that is still contaminating the silver. If some is being washed away, there will be some left. By washing until all color is gone, that means there is no more being washed away, and no more left in the silver. Now, in practice, there will still be some that just can't be washed away, but that's to be expected (can't get cemented silver above ~99.4%)

melting dish looks good! the scorch marks may not come off, it could be soot or stain or copper oxide (which I believe wouldn't react with nitric) and not borax. Either way, it wouldn't interfere with future melts. Putting the bath on low heat (not boiling) will speed up the dissolving.