4240. Carbonate of Magnesia

4240.    Carbonate of Magnesia. There are two simple carbonates of magnesia, the heavy and the light.

The heavy carbonate is prepared from a saturated solution of sulphate of magnesia, 1 part by measure; water, 3 parts; heat to the boiling point, then add cold saturated solution of carbonate of soda, 1 part; boil, with constant agitation, till effervescence ceases, then add boiling water, 100 parts, agitate well, decant off the clear liquid, drain, and wash the precipitate with hot water, in a linen cloth, and finish the drying by heating it in an iron pot.

The light carbonate is obtained from 4 pounds sulphate of magnesia, and 4 pounds 9 ounces carbonate of soda, each separately dissolved in 2 gallons water. Mix and boil the liquors, constantly stirring for 15 minutes; after subsidence, decant the clear, wash the precipitate with boiling water, and dry it. The carbonate of magnesia of commerce is usually made up into cakes or dice, while drying, or is permitted to drain and dry in masses, which are then cut into shapes with a thin knife. It is powdered by rubbing it through a wire sieve. (Cooley.)

4241. Sulphate of Magnesia

4241.     Sulphate of Magnesia. This is the well-known Epsom salts of commerce, called after the saline springs of Epsom, in England, from the waters of which it was originally obtained. It is prepared on the large scale from Dolomite, or magnesian limestone. Heat the mineral with sufficient dilute sulphuric acid to convert all its carbonate into sulphate of lime, wash out all the sulphate of magnesia with hot water, and, after defecation, evaporate and crystallize.

Or, from bittern. Boil the residual liquor, or mother-water of sea-salt, for some hours, skim, and decant the clear, then concentrate by evaporation, and run the solution into wooden coolers; in 1 or 2 days 1/8 part of Epsom salts will have crystallized out. This is called singles. By re-solution in water, and re-crystallization, doubles, or Epsom salts, fit for the market, are obtained.

4242. Sulphuret of Magnesia

4242.     Sulphuret of Magnesia. The sulphide, or sulphuret, is prepared by fusing together, in a covered crucible, 5 parts calcined magnesia and 4 parts sulphur.

4243. Chloride of Magnesium

4243. Chloride of Magnesium. Dissolve magnesia in muriatic acid, evaporate to dryness, add an equal weight of muriate of ammonia, project the mixture into a red hot platinum crucible, and continue the heat until tranquil fusion is attained. Pour out the fused mass on to a clean stone; and, when solid, break it into pieces, and transfer to a warm, dry bottle. (Cooley.)

Or: Dissolve magnesia in muriatic acid; evaporate to a specific gravity of 1.384; and put it, while hot, into a wide-mouthed flask to crystallize. (Paris Codex.) This chloride of magnesium is also called hydrochlorate or muriate of magnesia.