Introduction to the study of inorganic chemistry / by William Allen Miller.

  • Miller, William Allen, 1817-1870.
Date:
1871
Catalogue details

Licence: Public Domain Mark

Credit: Introduction to the study of inorganic chemistry / by William Allen Miller. Source: Wellcome Collection.

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    ])hie precipitate wliich tliey give with the red jirussiate (])otassic ferricyanide) in solution. If one of the ferrous salts be boiled with nitric acid, it is converted into a solution of ferric salt, while one of the lower oxides of nitrogen escapes. Ferric salts in solution are known by the rust)-brown precij)itate of hydrated feme oxide which they give with ammonia, by the blood-red solution produced by potassic sulphocyanide when added to an acid or neutral solution, by the bright Prussian blue precipitate occasioned by a solution of yellow potassic ferrocyanide, and by the bluish-black inky precipitate produced by tincture of galls in neutral solutions. This last is the colouring matter in ordinary writing-ink. Potassic ferricyanide gives no ])recipitate in ferric solutions, and thus may be used to distinguish them from those of ferrous salts. F.xp. 239.—Add to a solution of a ferric salt, mixed with a little solution of a salt of cobalt, a weak solution of ammonia, drop by drop, stirring the liquid between each addition, until the pre- cipitate just begins no longer to be dissolved. The solution will become of a deeper red or yellow tinge. Dilute the liquid freely with water, and then boil it; an insoluble basic salt of iron will be formed, and every trace of iron may thus be precipitated, whilst the cobalt will remain dissolved, and may be found by atlding a little more of ammonia. (55) 5. Chromium {Symh. Cr; At. JVt. 52-5) is never used as a metal, or even as an alloy, but is highly prized for the numerous brilliant-coloured compounds which it forms, d'he name chromium is derived from colour. It is a rather rare element, and is most usually found in the chrome ironstone (PeO, Cr-()3). The metal is ver)' hard and infusible. It is .sometimes obtained by heating chromic chloride with sodium. Chromium forms four well-known oxides: chromous oxide(CrO), which is unimi)orlant ; chromic o.xide{CxX)^, the basis of the common green or violet salts of the metal : it is prized as a green pigment for colouring porcelain (these two oxides corre-