Cyanoplatinous acid

Platini-, platinic, platini-, platinum (IV). -chlorid, n. platinic chloride, platinum (IV) chloride, -chlorwasserstoff, m., -chlorwasserstoffsaure, /. chloroplatinic acid, chloroplatinic (IV) acid, -cyanwasserstoffsaure, /. cyanoplatinic acid, cyanoplatinic(IV) acid, platinicyanic acid. 

Cyanoplatinous Acid, HaPt(CN)4, maybe prepared by decomposition of its mercuric5 or cupric 8 salt suspended in water by a current of hydrogen sulphide. On filtration and evaporation bluish black prisms are obtained, which deliquesce on exposure to moist air. The salt is easily soluble in water, alcohol and ether. At 100° C. it decomposes into platinous cyanide and hydrogen cyanide. Sulphuric acid converts it into platinous cyanide. The aqueous solution reacts strongly acid, decomposes carbonates, and has an acid taste. The alcoholic solution deposits a mirror of platinum on the containing vessel when heated. 

When a solution of barium platinocyanide is allowed to crystallise after adding a trace of barium cyanide or barium hydroxide to it, crystals of the green 8-salt axe obtained. If, on the other hand, a trace of hydrogen cyanide, hydrogen chloride, tartaric or acetic acid, or cyanoplatinous acid is present instead, crystals of the yellow a-salt are deposited. 

Platinum Tricyanide, Pt(CN)3, is obtained in a more or less pure condition as a yellow powder on heating cyanoplatinic acid to 120° C.4... 

Sulphur dioxide reduces the acid solution to cyanoplatinous acid. Heated to 120° C. the solid green acid is converted into a light yellow residue consisting mainly of platinum tricyanide, Pt(CN)3. 

Potassium tetracyanopalladate(II) when crystallized from water forms the 3-hydrate, which is a white crystalline salt, isomorphous with the corresponding rhombic tetra-cyanoplatinate(II). The 3-hydrate is efflorescent in air it loses two molecules of water of crystallization at 100° and the thii d at 200°. When the compound is heated to moderately high temperatm-es, it decomposes with the formation of palladium, cyanogen, and potassium cyanide. The 1-hydrate is readily soluble in water and in liquid ammonia and is somewhat soluble in alcohol giving colorless solutions in each case. The addition of dilute acids to potassium tetracyanopalladate(II) precipitates pal-ladium(II) cyanide, while boiling with concentrated sulfuric acid completely decomposes the compound. 

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