Does really silver dissolve in AR or not butcher pls?
- Thread starter Ariaana
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I have found that for what ever reason, some silver will stay in the A/R until you denox it (karet scrap). I can not say that I fully understand the mechanics, but, after I denox some silver chloride always falls out.
Silver (Ag) does not dissolve in HCl acid, but the acid can attack fine silver powders or if thicker the surface forming a crust of silver chloride, in aqua regia silver basically for the most part does not dissolve but will form silver chloride (AgCl) which is an insoluble fluffy white powder that takes time to settle, or if too much silver it can form a crust of passivated silver that protects the gold from the acid...
Basically you will not for any practical amount have silver (Ag), or silver chloride (AgCl) and gold (Au) both in solution at the same time.
Now with that said, in a highly concentrated aqua regia assisted by the very high chloride concentration or the high common ion effect, and the oxidizing environment of the acids a very tiny amount of Silver chloride (AgCl),(just enough to contaminate the gold), can be oxidized into a soluble solution of Dichlorosilver ions (AgCl2).
Once diluted with water and letting the gold chloride sit overnight the Dichlorosilver (AgCl2)is reduced to an insoluble white powder of silver chloride (AgCl) which will settle overnight as white powders to the bottom of the undisturbed flask or vessel...
Basically you will not for any practical amount have silver (Ag), or silver chloride (AgCl) and gold (Au) both in solution at the same time.
Now with that said, in a highly concentrated aqua regia assisted by the very high chloride concentration or the high common ion effect, and the oxidizing environment of the acids a very tiny amount of Silver chloride (AgCl),(just enough to contaminate the gold), can be oxidized into a soluble solution of Dichlorosilver ions (AgCl2).
Once diluted with water and letting the gold chloride sit overnight the Dichlorosilver (AgCl2)is reduced to an insoluble white powder of silver chloride (AgCl) which will settle overnight as white powders to the bottom of the undisturbed flask or vessel...
Thank you for the explanation butcher! I knew that the a bit of silver was staying in my solution until I diluted and denoxed, but now I get why, I think.
In very simple terms (what I understand), in a high chloride concentration, a bit of silver can remain dissolved. Chris (Goldsilverpro) experimented to find that by diluting concentrated AR to about a 3 to 1 concentration, the dissolved silver would precipitate as insoluble AgCl, and could be filtered off prior to dropping gold. Harold always precipitated from a very concentrated AR, so he implemented his ammonia wash to dissolve and eliminate any associated silver from his solutions.
Dave
Dave
The highest level of dissolved silver in chloride solution is obtained when the chloride level is 10% or above.
At lower chloride levels the silver becomes unstable and will proportionally precipitate out as the chloride level drops.
The precipitating silver will also co-precipitate silver which would normally remain in solution at that chloride level, it will also co- precipitate some gold values.
Deano
At lower chloride levels the silver becomes unstable and will proportionally precipitate out as the chloride level drops.
The precipitating silver will also co-precipitate silver which would normally remain in solution at that chloride level, it will also co- precipitate some gold values.
Deano
Deano said:
Interesting. 8)
The High chloride content or common ion effect can also apply to other solutions, for example, a highly concentrate heated solution of ferric chloride will attack silver and other base metals with a vengeance, besides forming silver chloride (AgCl) it will also form some of the soluble silver or dichlorosilver (AgCl2)...
