Notes.—Test complete washing by hydrochloric acid. Wash with water till zinc nitrate is removed. If zinc clings to silver wash with hydrochloric acid.
3. Suspend sheet of copper in bath for two or three days.
4. Acidify as nitric acid, precipitate as silver chloride by sodium chloride or hydrochloric acid, and reduce as vide III, below.
5. Immerse in bath two strips of copper attached to the poles of a Daniell’s or Smee’s cell. Silver deposited on the copper as in 3, above.
6. Add sodium bicarbonate or sodium hydrate. Reduce as 3 below, or if pure enough, dissolve precipitate at once in nitric acid.
7. Concentrate bath, make alkaline by sodium carbonate, and add aqueous solution of oxalic acid neutralised with sodium carbonate. Filter, dry, and fuse with equal weight of sodium bicarbonate.
8. Deposit, either with or without battery, on iron. (Iron can be obtained purer than zinc or copper, and possesses the additional advantage that the iron salts, as iodides, &c., are
all quite soluble). Fuse with potassium nitrate and sodium carbonate.
β. Renovated.
1. Dilute with three volumes of distilled water, expose to sunlight, filter, add sodium carbonate till slightly turbid. Expose to sunlight six hours more, filter, add sodium carbonate till silver all thrown down. Wash, precipitate by decantation, and dissolve in nitric acid. Filter again, make up to 35 grammes; neutralise, expose to sun a week, and bath is ready for use.