Page:Pharmacopoeia of India (1868).djvu/359

Rh

Phosphate of Lime, 3CaO, PO₅, or Ca₃P₂O₈, prepared by dissolving bone-ash in hydrochloric acid, precipitating with ammonia, and drying at a temperature not exceeding 212° F. Characters.—A light white amorphous powder, insoluble in water, but soluble without effervescence in dilute nitric acid. The solution continues clear when an excess of acetate of soda is added to it, but lets fall a white precipitate on the addition both of a little oxalate of ammonia, and of perchloride of iron. Tests.—Ten grains dissolve perfectly and without effervescence in diluted hydrochloric acid. The solution yields with ammonia a white precipitate, which is insoluble in boiling solution of potash, and when washed and dried weighs ten grains.

MAGNESIUM.

Symbol, Mg; At. weight, 12; or Mg = 24.

Magnesium, the metallic base of Magnesia; of a brilliant, silver-white colour, hard and ductile. Sp. gr. 1·743. Burns in oxygen, or in air, with brilliant light to Magnesia, MgO. Combined with sulphuric acid, magnesia forms a constituent of sea water and many mineral springs. It exists likewise to a considerable extent in certain limestones, and is present, though in small proportion, in animal solids and fluids, especially the urine. It is also found in the vegetable kingdom.

Magnesia, MgO, obtained by subjecting carbonate of magnesia to a heat sufficient to expel the carbonic acid