Chlorplatinic acid

Platinum tetrachloride or platinic chloride, PtCL, may be prepared by heating chlorplatinic acid in a stream of HC1 or chlorine. It has a reddish brown color, and on exposure to air it absorbs moisture, becoming bright yellow in color. It dissolves fairly well in warm water, the solution being strongly acidic, as is shown by the fact tli.it it liberates turban dioxide from the carbonates. The solution is reduced by iodine, thus PtCl, + I2 — PtCl2 + 2 IC1, a reaction used for the volumetric estimation of platinum. 

The fact that these acids are all dibasic proves that the acidity is not connected with the hydrogen of the hydroxyl groups, and by comparing the whole series from chlorplatinic acid to platinic acid, it is evident that the ionizable hydrogens are those combined directly with the positive central atom, platinum in this case. The salts of these acids have similar structures. 

The addition of hydrogen chloride to sulfur trioxide, becomes analogous to the addition of hydrogen chloride to platinic chloride, yielding in the first case, chlorsulfonic acid, HSO3CI, and in the second case, chlorplatinic acid, H2PtCl6. 

Carbon monoxide bears the same relation to formic acid that sulfur trioxide bears to sulfuric acid, or that platinic chloride bears to chlorplatinic acid, etc. Carbon monoxide also bears the same relation to the higher organic acids such as acetic, propionic, etc., acids that sulfur dioxide bears to the sulfonic acids, or that the anhydride of nitrous acid bears to the nitro compounds, etc. 

Xanthic acid was investigated by Couerbe. Zeise discovered thiocarbamic acid by the action of carbon disulphide on ammonia, the addition compound of ethylene and platinous chloride (Gekohltenwasserstoffes Chlorplatin), and mercaptan (from corpus mercurium captans), by distilling potassium hydrosulphide with potassium ethyl sulphate KKS +0211 0—... 

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