Chemical Aids to Art. 181 



wlio made coins of it, adopting the plan invented by the 

 English chemist, Wollaston, submitted the powder of pla- 

 tinum, as obtained by the chemical treatment of the ore, to 

 powerful pressure, arid to repeated blows, and also to the 

 influence of a very high temperature. By this process the 

 powder or fine particles of the metal may be made to cohere 

 into an uniform solid mass. It is thus that platinum is 

 fashioned into crucibles for chemists, stills for the purification 

 of sulphuric acid, foil, leaf, and wire for various useful pur- 

 poses. But we really must not dwell further upon these 

 interesting facts in the history of platinum, for our intention 

 is to describe something newer and less known. We purpose 

 giving the details of a very simple and beautiful process for 

 covering other metals with a delicate film of metallic platinum, 

 and so at once varying their appearance, and endowing 

 them with one of the virtues of this metal, namely, incorro- 

 dibility. 



We have before mentioned that although platinum does 

 not easily dissolve in acids, it can be induced to dissolve by 

 appropriate treatment. If a few grains of scrap platinum, 

 which may be purchased at the rate of about twenty shillings 

 the ounce, be warmed in a flask with a mixture of three parts 

 of hydrochloric (muriatic) acid and one part of nitric acid 

 (aqua regia), it will soon begin to disappear, dissolving in the 

 acids with a red-brown colour, not unlike that of dark sherry. 

 This liquid contains a compound of the metal platinum with 

 the non-metallic element chlorine. This compound is 

 generally called bichloride of platinum. It may be obtained 

 in the solid form by drying up, at a gentle heat, the acid 

 solution of the platinum scrap. This salt or compound of 

 platinum, may be thus prepared — 40 grains of the metal 

 yielding about 68 grains of the bichloride ; or it may be pur- 

 chased at a very moderate price. It cannot, however, be used 

 directly and without any further treatment for the purpose we 

 have in view, namely, the plating (or, rather, platinizing) of 

 various metals. The following directions will serve for the 

 preparation of a suitable solution for this purpose : — Dissolve 

 in one ounce of distilled water — 



60 grains of bichloride of platinum and 

 60 grains of pure honey. 



Add to the above solution three quarters of an ounce of spirit 

 of wine, and one quarter of an ounce of ether. The mixed 

 liquids, if not quite clear, must be filtered through a piece of 

 white blotting-paper. The objects to be platinized, which 

 may be of iron, steel, copper, bronze, or brass, are to be 

 thoroughly cleaned by washing them in soda, then in water. 



