PROPERTIES OF SULPHATES.

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Sulphuric acid united to alcalies, earths, &c. forms saline com-binations called SULPHATES.

PROPERTIES OF SULPHATES.

All the sulphates are insoluble in alcohol. Their solutions aredecomposed by a solution of barytes. They become convertedinto sulphurets by ignited charcoal at high temperatures, butthey are undecomposable by mere heat.

METHODS OF OBTAINING SULPHATES.

Sulphate of potash, soda, or ammonia may he obtained bysaturating these alcalies with sulphuric acid, evaporating the so-lution and crystallizing it. Sulphate of magnesia, and sulphateof alumine may be produced in a similar manner. Sulphate oflead may be obtained by pouring sulphuric acid into a solution ofacetite of lead, the sulphate of lead precipitates. Sulphate ofzinc is produced by dissolving this metal in diluted sulphuricacid and subsequent evaporation and crystallization. Sulphate ofnickel, sulphate of bismuth, and sulphate of cobalt, are pro-duced by dissolving the metals, by the assistance of heat, in sul-phuric acid, and proceeding as before.

Sulphate of iron is obtained by dissolving iron filings in dilutedsulphuric acid, evaporating the solution and subsequent crystalli-zation. This salt, if exposed to the air, soon becomes coveredwith a yellowish crust, because it absorbs more oxigen and be-comes partially converted into an oxi-sulphate of iron, whichis of a red colour, uncrystallizable, and soluble in alcohol jit may be deprived of its excess of oxigen by passing a currentof sulphurated hidrogen gas through it.