13enigma said:
Sodium chloride
Sodium carbonate
Sodium sulfide
Etc.
For electroplating.
I just want to keep it safe and I don't want to produce harmful gases that I cannot contain.
What is the best electrolyte you used?
I'm trying to silver electroplate a copper plate by using a silver plate at the anode
None of the chemicals you mentioned will even come close to act as a proper matrix for depositing satisfactory silver plating. By satisfactory, I mean, at least, a deposit that will stick to the copper without peeling off and will be smooth and, maybe, bright and of a desired thickness obtained within a reasonable amount of time. All plating solutions require a substantial amount of the metal to be plated (in this case, silver) to be dissolved in the solution before any plating can be done.
The choices for a good Ag electrolyte makes up a very short list. For at least a century, almost all of the silver commercially plated was plated from cyanide solutions. Since about the mid-1970's, because of demands made by the government and "green" people, companies have developed non-cyanide solutions. These are proprietary and secret and their formulas are not divulged to the public. Following are 2 non-cyanide formulas given by Goran Budija on the finishing.com forum. I haven't used these and I have no idea as to the quality of the deposits. I would guess, however, that a deposit from a typical cyanide bath would be superior to that deposited from a non-cyanide bath, whether proprietary or home-made. For that reason, I would also guess that cyanide solutions are still the most common type silver baths used in industry - probably by far.
"Ferrocyanide bath:
10 gms silver chloride
20 gms potassium ferrocyanide
20 gms potassium carbonate
1 lit water, stainless steel anodes
Pyrophosphate bath:
15 gm silver(in nitrate or phosphate salt)
100 gm potassium pyrophosphate
25 gm ammonium carbonate
1 lit water
Ferrocyanide-sulphite bath:
add 40 gm sodium sulphite to previously described ferrocyanide bath"
Notice that all decent plating solutions are composed of multiple ingredients of somewhat exacting quantities. Every ingredient will only work well within a certain concentration range that is obtained by experimentation. You can't just throw something together and expect it to work. All successful plating solutions are the result of many, many hours of experimental research and their formulas are quite exacting. Also, parameters like solution temperature, agitation, power supply ripple, anode size and composition, and current density, when not correct, can alter the deposit characteristics considerably. You also must know how to prepare the specific metal that you are plating the silver onto - if you do this wrong, the silver won't stick to the copper. The learning curve on plating is probably as long as that of refining.
There are very few types of silver solutions I know of that will plate a good sound deposit. Of these, the only one I know of that will, at the same time, dissolve silver from a anode in order to replenish the silver that has been plated out, is a cyanide solution. With all others, inert, non-dissolving anodes, like stainless steel or platinized titanium, would be used. With these inert anodes, the silver in the solution will decrease and you'll continually have to add more silver salts to the solution.
If you're serious about this, you should buy a ready made solution. Although these are more expensive than a homemade solution, they end up cheaper because, unlike homemade solutions, they work (if you totally follow the instructions). If you want a super thin deposit, solutions are available from a jeweler's supply. For thicker deposits and more professional solutions, a good company that sells mainly PM solutions is Technic, Inc.
