l leaped before I looked. Help.

[theblueletters]

I've been a jeweler for quite some time now though I have a BA in Chem with a concentration in organic chemistry. That being said I should have been smarter that this .... between my wife and I (she's a print maker; woodcut, silk screen, intaglio etc) we have a fair collection of acids and bases and I got over excited and I disolved between an once and and half ounce of what was mostly sterling and a little fine silver in around 600 mL of HNO3.

I was looking for a quick solution b/c I just started a new job and have been low on time and money.

Well my problem was that I thought, after a quick filtering to clean my solution, I'd be able to use a graphite rod as an anode and collect along a fine silver cathode. NOW at this point I've used every conductor I can think of an they're all just making my solution dirty. The one exception is more silver but I'm not really sure I'm getting out more then I'm putting in.

Apparently the ability of nitric acid to dissolve EVERYTHING slipped my mind. I can follow the AgNO3 to AgCl to AgO procedure I found here but id really rather some advice on an around the house anode that doesn't involve gold or platinum which seem to be the only elements standing up to HNO3. If I can just get a solid anode I can finish what I started and take my time next time.

If anyone can help me out of a jam this once I'd be greatly appreciative. Hope to hear from someone soon.
Thanks,
Andrew

 

[samuel-a]

theblueletters

Fisrt thing, you might want to do is a search about "silver cell".
All of the; What? How? and Why? have been answered before.

With that said, you need to remember that electrolytic cell is a continuous REFINING process, where new silver is being dissolved at one end, and pure silver is deposited out on the other. This process is not suitable for a batch recovery project. think about it, you will not make a fruit salad using tomatoes and onions, right?

You are looking to deplete the silver off the solution, there are much better ways to do that.
In this case i would suggest the simplest one, filter again to clean all of the solid junk that was left from anode.
Then hang a piece of solid copper to cement out the silver.

Spelling

 

[Harold_V]

What Sam said. Use a piece of copper, after filtering the solution well. I suggest you avoid the use of wire, which can be difficult to remove when all of the silver is down. It's known to break up in tiny pieces. Resulting silver can be expected to be in the range of 99% pure, assuming it is well washed. Tap water is acceptable for the wash, assuming all of the silver is down.

Harold

 

[goldsilverpro]

You're kind of in between a rock and a hard place with this.

It only takes about 45 ml of conc. HNO3 to dissolve 1 oz of sterling. Therefore, you still have 550+ ml of free nitric in the solution. Therefore, if you try to cement the silver with copper, no silver will cement until enough copper (about 140 g) is dissolved to eliminate the free nitric. To prevent crystallization of the copper nitrate produced, the nitric will have to be diluted first with distilled water - at least 1/1 and maybe more.

Electrolysis won't work because, with all that free nitric, the silver will re-dissolve as fast as it plates out. Since H+ ion is continually produced from water splitting at the inert anode, you would have an endless cycle of deposition and re-dissolving. The black you got is probably from the graphite breaking down.

Although AgCl is not my favorite thing to work with, you could make it easily with no interference from the excess HNO3. To ppt all of the silver as AgCl, you will most likely use an excess of Cl- ion. Therefore, the resulting HNO3/Cl- solution will likely be unusable unless you use it to make aqua regia sometime in the future.

 

[goldenchild]

Although AgCl is not my favorite thing to work with, you could make it easily with no interference from the excess HNO3. To ppt all of the silver as AgCl, you will most likely use an excess of Cl- ion. Therefore, it will likely be unusable unless you use it to make aqua regia sometime in the future.

Is this assuming HCL is used to drop the AgCl or will NaCl have the same effect? It'd be a shame to waste a half liter of HNO3.

 

[goldsilverpro]

Although AgCl is not my favorite thing to work with, you could make it easily with no interference from the excess HNO3. To ppt all of the silver as AgCl, you will most likely use an excess of Cl- ion. Therefore, it will likely be unusable unless you use it to make aqua regia sometime in the future.

Is this assuming HCL is used to drop the AgCl or will NaCl have the same effect? It'd be a shame to waste a half liter of HNO3.

Same in both cases - they both will put Cl- in the solution. He could carefully calculate and only add enough Cl- to ppt, say, 90% of the silver. That way, there would be no excess Cl- in solution and he could use it in the future to dissolve more silver. Or, he could dissolve another 12 oz (approx.) of sterling in it right now and then cement the silver.

The finely divided graphite in the solution could cause a problem, since it doesn't settle or filter easily. It would certainly be best to remove it before doing anything, however.

 

[theblueletters]

Thank you all for the help. The length of response between my question and response to this post ought to indicate how much free time I have. I suppose I'll end up cementing out the silver via Cu or using NaCl to create insoluble AgCl. After all what I really need is to be able to send my silver to a refiner in trade for sheet and wire and its not doing me any good hanging out as a blue liquid in my studio. Thank you all very much for the assistance.
Andrew

 

[nickvc]

Andrew not wanting to be rude but with the amount you have the cost of assaying the material may outweigh it's value. You might do better to recover your silver and re alloy it at say 95% and add pure copper to make it near stirling again and re working it yourself. I know new silver sheet and wire is expensive but the value of your scrap is very small so I'd try to re work it to minimise losses.