A treatise on chemistry. Vol. II, Metals. Part II / by H.E. Roscoe & C. Schorlemmer ...

  • Henry Enfield Roscoe
Date:
1880
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Licence: Public Domain Mark

Credit: A treatise on chemistry. Vol. II, Metals. Part II / by H.E. Roscoe & C. Schorlemmer ... Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

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    Potassium permanganate is isomorplious with potassium per- clilorate, with wliich it crystallises in all proportions. The crystals are almost black, and when freshly prepared possess a green metallic lustre, which however on exposure to the air becomes of a steel-blue tint without any further alteration in the salt taking place. The crystals have a specific gravity of 27, and yield a red powder. They dissolve in fifteen to sixteen parts of cold water (Mitscherlich), forming a deep purple-coloured solu- tion. When concentrated sulphuric acid is poured on to these crystals they decompose with evolution of light and heat evolv- ing ozone and giving rise to violet-coloured vapours (Wohler). On heating to 240° they decompose as follows : 2 KMnO^ = KgMnO^ + MnO.^ + Jones ^ has shown that hydrogen, phosphine, and other reducing agents decompose potassium permanganate, and that oxygen gas is evolved together with carbon dioxide when sul- phuric acid acts on the permanganate in presence of oxalic acid. Mixed with sulphur or phosphorus, a material is obtained which takes fire or explodes violently ou percussion, and a mixture of the salt with charcoal burns like tinder. Sodium Permanganate, NaMn04, is obtained in a similar way to the potassium salt, and is distinguished from it by being deliquescent, and, therefore, crystallising with difficulty. Ammonium Permanganate, ^H^nO^ is obtained by the decomposition of the potassium salt with ammonium sulphate. It is isomorphous with potassium permanganate, and decomposes readily on heating. Barium Permanganate, Ba(Mn04).,, forms hard, almost black prisms, soluble in water. It is obtained by passing a current of carbon dioxide through water containing barium manganate in suspension, or by the action of barium chloride on silver permanganate. Silver Permanganate, AgMnO^, separates out in large regular crystals when warm solutions of nitrate of silver and potassium permanganate are mixed. It dissolves in 190 parts of water at 15°, and is much more soluble in warm water. The solution decomposes on boiling. Permanganic Oxycliloridc, IMnO^Cl. This chloride of perman- ganic acid was first prepared by Dumas : ^ he did not however analyse the compound, but from its mode of decomposition con- 1 Chcm, Soc. Journ. 1878, 95. ^ Ann. Chim. Phys. [2], xxxvi. 81.
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