| 摘要 |
1,217,414. Silver treating composition; Electrolytic detarnishing of Ag. J. GODDARD & SONS Ltd. Aug.6, 1969 [June 29, 1968], No. 31214/68. Headings C7B, C7E and C7U. A silver detarnishing, cleaning, and protecting solution comprises an acid stronger than hydrosulphuric which does not in aqueous solution attack Ag, at least 1% of a soluble compound capable of forming a soluble complex with Ag<SP>+</SP> leaving substantially no Ag<SP>+</SP> in aqueous solution, and from 0À5-2À0 wt% of an organic compound containing an -SH group and capable of forming a transparent colourless protective layer. The acid may be H 2 SO 4 , HCl, H 3 PO 4 , acetic, citric or tartaric, the complexing agent may be thiourea or thiosemicarbazide, and the -SH compound may be stearyl or cetyl mercaptan or thioglycollate. The solution may contain an alcohol, e.g. i-PrOH, and a non- ionic or cationic emulsifying agent such as an ethylene oxide-alcohol or -phenol condensate or an ethoxylated long chain aliphatic amine. The solution is applied by dipping or spraying, or the Ag and any secondary metal associated therewith may be placed in electrical contact with a more electro-positive metal in the solution (e. g by putting the Ag articles in an Al basket which is immersed in the solution contained in a PVC or polyethylene vessel) or the Ag article may be made the cathode in an electrolytic cell containing the solution. |
