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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 chlorine is generated in leaden vessels, heated part by measure; water, 3 parts; heat to the by steam, and the gas, after passing through boiling point, then add cold saturated solu- water, is conveyed by a leaden tube into an tion of carbonate of soda, 1 part; boil, with apartment built of silicious sandstone, and arconstant agitation, till effervescence ceases, ranged with shelves or trays, containing then add boiling water, 100 parts, agitate well, fresh-slacked lime, placed one above another 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 about an inch asunder. The process must be continued for 4 days to produce a good article of chloride of lime. During this time the lime is occasionally agitated by means of iron rakes, the handles of which pass through boxes of lime placed in the walls of the chamber, which act as valves.