188
ELEMENTS OF MATERIA MEDICA.
Properties. —In its general properties animal charcoal agrees withcharcoal procured from wood. The decolorizing powers of the formerare, however, much superior to those of the latter.
Composition and Purification. —Animal charcoal, prepared bycalcining the bones of the ox, sheep, and horse, consists of the followingingredients, (Dumas, Traite de Chimie , t. i., p. 450):
Common Bone Black...100*0
For the ordinary purposes of the arts, as sugar refining, this impureanimal charcoal answers very well, because the earthy salts in no wayaffect the process. But in various pharmaceutical operations the pre-sence of phosphate and carbonate of lime would preclude the use ofanimal charcoal, on account of the free acid in the liquids to be deco-lorized. Hence the necessity of the purification of animal charcoal.
In the London Pharmacopoeia purified animal charcoal (carboanimalispurificatus) is ordered to be prepared by digesting for two days,with a gentle heat, a pound of animal charcoal in a mixture of twelvefluid ounces of hydrochloric acid and the like measure of water, fre-quently shaking them. After pouring off the supernatant liquor thecharcoal is to be washed with water until no acid is perceptible, andthen dried.
In the above process the hydrochloric acid dissolves the phosphate oflime and decomposes the carbonate of lime and sulphuret of calcium,evolving carbonic and hydrosulphuric acid gases, and forming chlorideof calcium, which remains in solution.
Purified animal charcoal causes no effervescence when mixed withhydrochloric acid, nor is any precipitate produced by the additionof ammonia or its sesquicarbonate to the acid. For effervescence wouldindicate the presence of carbonate of lime, while a precipitate withsesquicarbonate of ammonia would shew either phosphate or carbonateof lime : if phosphate, caustic ammonia would also occasion aprecipitate.
Animal charcoal, when deprived of its saline matters, usually containstraces of nitrogen. Dobereiner , indeed, supposed it to be a kind of sub-nitruret of carbon composed of one equivalent or 14 parts of nitrogen,and six equivalents or 36 parts of carbon. Bussy, however, has shownthat though animal charcoal retains its nitrogen with considerable obsti-nacy, yet that the latter may be separated by heat.
Physiological Effects. —The remarks already made in reference tothe physiological effects of wood charcoal, apply equally well to animalcharcoal.
Uses. —The principal use of animal charcoal is as a decolorizingagent in various pharmaceutical processes, as in the preparation ofsulphate of quinia, hydrochlorate of morphia, veratria, &c. The theoryof its efficacy is imperfectly understood. The superior value of animalto vegetable charcoal is usually referred to the minute separation of thecarbonaceous particles effected by the presence of other matters, as of