Syn. Glauber's Salt.

Preparation

Though sulphate of soda exists in nature, in certain springs and ponds, it is always obtained for use artificially, being usually the residue, or an incidental product of chemical processes, intended for the preparation of some other substance. Thus, it is left when common salt is decomposed by sulphuric acid in the process for procuring muriatic acid, and is obtained through the reaction of the same materials, as one of the steps in the manufacture of carbonate of soda on the large scale.

Properties

Sulphate of soda is in large, six-sided, beautifully transparent, striated crystals, which effloresce rapidly on exposure, and are almost always partially effloresced as found in the shops. in time, it is thus completely deprived of its water of crystallization, and falls into an opaque, white powder. it is inodorous, of a cooling, bitterish, saline, and very disagreeable taste. it varies extremely in solubility with the temperature, requiring near the freezing point about twenty parts of water, and at 91° F., when its solubility is greatest, only about one-third of its weight; while at 60° it requires three times its weight, and at 212° its own weight. Alcohol does not dissolve it. At a moderate heat it liquefies in its water of crystallization, upon the continuance of the heat dries, and at a red heat melts, and loses all its water, amounting to somewhat more than 55 per cent. it consists of 1 equivalent of acid, 1 of base, and 10 of water. Of course, it has in its effloresced state about twice the strength of the crystals.

Incompatibles. it is decomposed by carbonate of potassa, and the soluble salts of lime or calcium, baryta or barium, lead, and protoxide of mercury, and also by solutions of nitrate of silver containing fifteen grains or more to the fluidounce.

Medical Uses

This salt was discovered about the middle of the seventeenth century by Glauber, after whom it was named. it has the characteristic effects of the saline cathartics, and may be used for all the purposes which they, are given to fulfil. it was formerly in common use, but has been almost entirely superseded by sulphate of magnesia. Some, however, by a singular idiosyncrasy, prefer its taste to that of the latter salt; and these should always be gratified in their choice. The medium full dose of the crystals is an ounce. When taken, it should be dissolved in water a little heated, by which its solution is much more speedily effected than by cold water.