Elements of modern chemistry by unknow

Author:unknow
Language: eng
Format: epub
Tags: Chemistry
Publisher: Philadelphia [etc.] J. B. Lippincott company
Published: 1900-03-25T05:00:00+00:00

Between 7 and 20°, manganous sulphate crystallizes with 5 molecules of water, like cupric sulphate, with which it is then isomorphous.

Between 20 and 30°, it is deposited in oblique rhombic prisms, according to Marignac, which contain only 4 molecules of water.

All of these crystals are pink-colored, and their color is deeper as they contain more water of crystallization. They are very soluble in water.

MANGANOUS CAEBONATE.

MnC03

The residues from the preparation of chlorine may be used for making this salt. They are evaporated, without filtering, in a porcelain capsule, with frequent stirring, and the dry residue is calcined with an excess of manganese dioxide. The ferric chloride which was mixed with the manganous chloride is decomposed or volatilized during this operation. Ferric oxide remains, mixed with the excess of manganese dioxide and the manganous chloride, which resists the heat. The latter is extracted by exhausting the mass with boiling water. A rose-colored solution is thus obtained which often contains a small quantity of cobalt chloride. The latter is precipitated as sulphide by adding little by little a solution of sodium sulphide. As soon as the precipitate, which is at first blackish, begins to assume a flesh tint, the liquid is filtered and precipitated by sodium carbonate.

Manganese carbonate constitutes a white powder with a paW rose tint. When heated in contact with air, it gives up carbonic acid gas and is converted into red oxide of manganese.

Characters of Manganese Salts.—The salts of manganese are colorless or have a light pink color. Their solutions are not precipitated by hydrogen sulphide. Ammonium sulphide gives a flesh-colored precipitate ; sodium carbonate, a dirty white. Potassium hydroxide produces a dirty white precipitate of manganous hydroxide, which rapidly becomes brown by absorbing oxygen from the air.

When heated in the blow-pipe flame with a small quantity of potassium hydroxide or nitrate, the salts of manganese give a bead which dissolves in water with a green color (manganate).

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