204 MEDICINAL SALTS 



chemically and physiologically those of magnesium. Carbon- 

 ate of lime is the great source of the calcium salts. They 

 are detectable in solution by their yielding no precipitate 

 with hydrochloric acid, hydrogen sulphide, or ammonium 

 hydro-sulphide ; a white precipitate with an alkaline 

 carbonate ; an immediate and abundant white precipitate 

 with oxalic acid, insoluble in acetic but soluble in hydro- 

 chloric and nitric acids ; but no precipitate with ammonia, 

 which precipitates the compounds of aluminium and mag- 

 nesium. Calcium salts give a reddish-yellow tinge to flame. 

 Calcium compounds have little affinity for animal textures, 

 and are slowly absorbed and diffused. As with other metals, 

 the oxide and carbonate nearly resemble each other, and 

 are antacid and desiccant. The phosphate, or glyeero- 

 phosphate is prescribed as a restorative and tonic in many 

 forms of malnutrition. The hypophosphite is recommended 

 in anaemia and debility. The chloride has been given, 

 though seldom with success, to reduce enlarged lymphatic 

 glands, and to promote the healing of ulcers. The presence 

 of calcium is necessary to the coagulation of milk by rennet, 

 and also to the clotting of blood. For this reason the 

 chloride is often given for a few days to increase the plasticity 

 of the blood and thus lessen risk from haemorrhage in 

 operations. Calx chlorinata is irritant, disinfectant, and 

 deodorant, owing to its chlorine content. Calx sulphurata, 

 consisting of calcium sulphide with calcium sulphate and 

 carbon, has been credited with the power of checking forma- 

 tion of carbuncles, boils, and acne pustules. Calcium sul- 

 phate rendered nearly anhydrous by heat, is employed in 

 making plaster bandages for fractures. 



CALCIUM OXIDE. Lime. Quick-lime. Calx. CaO. 



When limestone, chalk, marble, or other form of calcium 

 carbonate is mixed with coal and thoroughly burned, its 

 carbonic acid is driven off, and the metallic oxide or quick- 

 lime is left. It occurs in greyish- white irregular masses, 

 has an alkaline, caustic taste, and great affinity for water. 

 It combines with about 24 per cent, of water, giving off 

 much heat, and forming calcium hydroxide, or slaked lime, 



