Extracting Silver.
Submitted by Anonymous on 17 September 2004 - 11:45am.
Hi. this is my first post, but i'm determined to find some answers. :lol: Now, i've acquired some silver solder and it's, what, some 67% silver. So i've found out that silver boils at some 2000+K. So is there a way to extract the silver from this silver solder by fractional distillation in a lab?

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well 2000K is damn hot....
....what temperature does glass melt at, eh...? lol
I'd imagine that a better method would involve some kind of chemical process you've got silver and what else in there? tin? lead?
Probably better to react the solder with some reagent which will complex out the silver, and leave the other metals behind.....
or at least form compounds with all the metals, but these compounds are much easier to separate physically
(eg perhaps you'd find that silver chloride would preciptate out versus tin chloride? then you could electrolyse the AgCl and get silver off at the anode..... although I'm completely guessing as to whether the chlorides would be the most suitable...... you see the general principle, though? you want to react the solder with X, to form an AgX and SnX2, where the two of those have suffuiently different solubilities or sthg so that you can separate them easily without having to heat anything to 2000K ! )
yes there is tin in it. bit i,m unfamiliar with the method you are suggesting. would you care to explain?
I thought I just did? lol
What bit didn't you understand...?
For Ag solder, chemical separation is probably best; dissolve the solder in nitric acid; you need about 1.25 to 1.5 moles of HNO3 for every mole of Ag/Sn alloy. The Ag can be precipitated 2 ways. Pure Ag can be extracted by placing a Cu wire in the solute until the solution turns sky blue and no more Ag crystals form on the wire (you should use very heavy gauge wire to prevent its complete dissolution in the acid mixture). Lift the wire out gently so as not to disturb the Ag crystals and gently rinse them off in a filter paper with distilled H2O. You will have pure crystals of Ag that can be melted further.
You will get more of the Ag if try technique #2; add dilute HCl (hydrochloric acid muriatic acid at your pool supply shop) until the curdy white precipitate stops forming; filter the solution for the curdy white precipitate and wash with distilled water. The solute should be a mixture of Sn ions and nitric acid; the filtrate should be AgCl. Place this in a boat (that's a porcelain lab dish (a Corningware casserole from Cost Plus or Wall Mart will do) and heat the hell out of it. AgCl is rather unstable, mixed with gelatin it is coating of photographic paper; exposure to light drives of the Cl leaving pure finely divided Ag as the dark areas of black n white photos. On exposure to light, your white curds will slowly turn purplish black as the Cl is driven off. Heat just hastens the process, don't heat too much, hot Ag has an affinity for O2 (which is why Ag amalgam fillings eventually crack in your teeth; they absorb O2 and swell -- the addition of Sn and Sb is alleged to retard the process, but then of course you have Sb and Hg inside your mouth (my dentist tells me that studies have failed to demonstrate any deleterious effects from this but he adds "I wouldn't want it in my mouth"). Heating to drive off the Cl should leave you with fairly pure Ag.
If you wish, you may cover the AgCl with a thick layer of ground charcoal; it will absorb some of the Cl and prevent the O2 from reaching the Ag if you heat it to the melting point. Upon cooling, you will have an ingot of Ag.
On other thing, if after dissolving the Ag solder in nitric acid, the solution isn't clear, you have other species in the solution. Traces of Cu (added as a hardener) make the solution bluish; this isn't anything to worry about. If the solution become a rosy pink somebody has added rhodium; if it turns an intense persistent red (not to be confused with the momentary reddish-brown of nitric acid as it dissolves the Ag -- there should be red-brown NO2 gas evolved, that's just highly concentrated smog, it is of course damaging to you lungs -- did I mention that this should be done with adequate ventilation and not in a closed bathroom at midnight?) then you have palladium in the solution; right now, palladium is more valuable than platinum and by all means save the solute! :roll:
alright. i get it. but i just found out that there is copper and zinc together with the silver in the solder (no Sn). now is that going to affect the results in any way :?:
if its less then 5% or so it should be fine, I would imagine.
Both ZnCl2 and CuCl/CuCl2 are soluble, so extraction by dissolving the solder in nitric acid and then precipitating the chloride should work fine. Instead of hydrochloric acid, you could use salt water which would add Na to the solute and produce a less hazardous product than nitric acid, you would have in effect a solution of sodium, zinc and copper nitrate.
i last thing, would the metal be pure enough for electroplating?[/i]
If you intend to electroplate, purification may be an unnecessary step. Electrodeposition has traditionally been one of the techniques used to prepare ultrapure samples of metals. The impure metal is used as the anode and a small pure sample serves as the cathode and the electric current is passed through depositing pure metal on the ode.
With silverplating, the thing you need to worry about is crystalization. Silver is often deposited in crystaline form that is unacceptable. The solution for plating is usually sodium argenticyanide, Na.Ag(CN)2 made by dissolving Na(CN) in AgNO3. First Ag(CN) is formed and precipitates out, but the Ag(CN) is dissolved in further Na(CN) to give soluble Na.Ag(CN)2. Gelatin is added to the solute to minimize the possible crystalization of the deposited Ag.
If you intend to electroplate, purification may be an unnecessary step. Electrodeposition has traditionally been one of the techniques used to prepare ultrapure samples of metals. The impure metal is used as the anode and a small pure sample serves as the cathode and the electric current is passed through depositing pure metal on the anode.
With silverplating, the thing you need to worry about is crystalization. Silver is often deposited in crystaline form that is unacceptable. The solution for plating is usually sodium argenticyanide, Na.Ag(CN)2 made by dissolving Na(CN) in AgNO3. First Ag(CN) is formed and precipitates out, but the Ag(CN) is dissolved in further Na(CN) to give soluble Na.Ag(CN)2. Gelatin is added to the solute to minimize the possible crystalization of the deposited Ag.