To cover metals with a layer of tin by an immersion process, they are dipped, after being well cleaned, in a boiling bath, containing ammoniacal alum, 535 parts; water, 870 parts; proto-chloride of tin, 31 parts.
(2) Another bath for tinning is the following: Bitartrate of potash, 435 parts; water, 870 parts; proto-chloride of tin, 31 parts.
(3) To cover metals with a layer of tin by means of electricity, the following bath is prepared: Pyrophosphate of potash, 400 parts; proto-chloride of tin, 150 parts; water, 500 parts. The anode is an ingot of pure tin (Banca); the negative is a zinc.
(4) A bath is prepared by leading chlorine through a concentrated solution of chloride of tin until saturated. The excess of chlorine is then driven away by heating the solution after adding to it ten times its volume of water and filtering. The pieces which have to be tinned are cleaned in dilute acid, polished with fine sand, washed, and then, suspended to zinc wire, are left for ten or fifteen minutes in the galvanizing bath. This method has. the advantage that the bath becomes charged with chloride of zinc very soon, and that the tin salt must be often added.
(5) Tartaric acid, 62 parts; water, 3,000 parts; soda, 90 parts; proto-chloride of tin, 90 parts.