262 VII. EARTHS AND ALKALIES.— 



by washing and making into large balls for cheap white paint, or 

 into small drops for medical use. 



Creta pr^cipitata. Precipitate a solution of muriate of 

 lime by a solution of subcarb. of soda in water, and wash the 

 sediment. — Officmal preparation, Mistura cretse, i. £. ; Hydrar- 

 gyrum cum creta, L. ; Pulvis cretae compos., L. E, ; Pulvis opia- 

 tus, E. 



Magnesia alba, Subcarbonate of magnesia. Magnesia, P. D. 

 Magnesice carbonas, M. subcarbonas. Obtained by precipitating 

 the bittern, or liquor, left in the boiling of sea-water after the 

 common salt has been separated, by a ley of wood ashes or sub- 

 carb. of potash. With respect to its use, it is antacid, and laxa- 

 tive when it meets with an acid, and may be given in the dose of 

 3ss to 3ij in water. — Officinal preparation. Magnesia, L. E. D.; 

 Hydr. cum magnesia, Z). 



2. Epsom salt 12 oz., potas. subcarb. 9 oz., water 3 gall. ; mix: 

 is a mixture of the hydrate and carbonate of magnesia. 



Henry's magnesia. Epsom salt 561b., dissolve in water, and 

 precipitate with subcarb. of soda, q. s. dissolved in water ; wash 

 the sediment well, and finish the washing with rose-water. Sub- 

 carbonate of magnesia is made up while drying, either into large 

 cubes with the edges bevelled, or in small dice : is powdered by 

 being rubbed through a sieve ; antacid, laxative, lithontriptic, 

 3ss — 3ij ; mixes well with milk, but not with water, sometimes 

 occasions flatulence. 



Calcined magnesia. Oxide of magnesium, Magnesie caustique. 

 Magnesia usta. Magnesia, P. L. and P. E. Expose subcarb. of 

 magnesia to a red heat for two hours, or until it exhibits a pecu- 

 liar luminous appearance: produces about half its original 

 weight ; antacid, laxative, 5ss — 3ij ; does not occasion flatulence, 

 but is not so soluble in the stomach as the other; it absorbs 

 scarcely any carbonic acid by exposure to the air ; equivalent 1 -5. 



M AGISTERS OF ALUM, Earth of Alum, Pure alumine, Oxide of 

 aluminium. Dissolve alum in water, and add to the solution 

 ammonia water sufficient to precipitate the earth ; wash it well, 

 and dry. 



2. Dry ammoniacal alum, rub it to powder, and keep it red 

 hot in a crucible for some hours. 



Gelatinous alumine, Hydrate of alumine. Pure alumine, 

 not dried, but in a moist state : used to mix with oxide of cobalt 

 and other colouring oxides as a basis for the colour. 



Baume''s alum white. Roman alum lib., honey half a lb.; 

 dry, powder, and calcine in a shallow dish to whiteness; wash 

 and dry : a beautiful white, even with oil. 



