Loncl. Edin. Dub.

Syn. Charbon de bois purifie (F.), Reine Kohle (C), Koole (Dutch), Kol (Swed.), Carbone di legna (I.), Carbon de lena (S.), Adapoo Currie (Tam.) Fuhm Chobic (Arab.), Zegal Chobic (Pers.), Koyla (H.), Arang (Malay).

Charcoal is prepared for the common purposes of fuel, by piling up billets of wood into conical heaps, which are covered with earth and sods, and then burned, with as little exposure to the action of the air as possible: but for the preparation of the finer kinds of charcoal, fit for medicinal use, the following process is employed. The wood to be charred is put into a large cast-iron cylinder, fixed in masonry over a grate. This cylinder terminates at one end in a curved pipe, and the other end is furnished with a door, which is accurately closed after the wood is introduced: a fire is next lighted in the grate; and the water, empyreumatic acid, and volatile parts of the wood, are driven off through the curved tube by the heat, which is increased until the contents of the cylinder become red-hot. The fire is then withdrawn, the cylinder is allowed to cool; and a black, shining, pure charcoal is thus obtained.l Ivory and bone shavings, treated in the same manner, make the preparation termed Ivory Black, For internal use, however, it is perhaps necessary to have wood charcoal still purer; and to effect this, the process of M. Lowitz is to be preferred. The charcoal is to be reduced to fine powder, and put into a crucible (so as to fill it), on which a pierced cover must be luted.

This vessel is then to be heated red-hot, and kept so, as long as a blue flame appears to issue from the hole in the cover; and when this stops, it is to be taken from the fire, cooled in a dry place, and the charcoal, instantly, put into well-stopped bottles for use.2

In whatever manner prepared, the purest charcoal contains, generally, about one fiftieth of its weight of earths, salts, or metallic matters; its other constituents are, according to Doberiener3, 68.4 of carbon, with 1.5 of hydrogen, and a minute portion of oxygen. The salts and earthy matters can be separated by boiling the charcoal with diluted muriatic acid in excess; then washing the charcoal on a filter with boiling water, until the fluid passes free from acid and throws down no precipitate with oxalate of ammonia. The powder is finally to be dried in a stove.

Qualities. - Pure charcoal is inodorous and insipid; black, shining, and brittle. It is a good conductor of electricity. Its sp. gr. is about 3.5. When newly prepared, it absorbs air, gases, moisture from the atmosphere, and liquids, so as to increase its weight from 10 to 18 per cent., according to the kind of wood from which it is made.4 It is insoluble in water and every other fluid5; and is easily pulverized. When ex-

1 This process was invented by Bishop Watson, for the use of the gunpowder manufacturers, who require a very pure charcoal. -Aikin's Chem. Dict., art. Carbon.

2 Crell's Chymical Journal, ii. 270.

3 Schweizgers Journal, xvi. p. 92.

4 From the experiments of Allen and Pepys, charcoal from fir gained 13 per cent.; from box, 14; from beech, 16.3; from oak, 16.5; from mahogany, 18.

5 There is, nevertheless, a quack preparation for cleaning the teeth, sold under the name of "Concentrated Solution of Charcoal." eluded from air, it is not affected by the highest degree of heat. When pure and well washed, so as to destroy all the earths and salts, it corrects the foetid odour of putrefying animal and vegetable substances; and destroys the odour, taste, and colour of some, particularly of mucilages and oil, and matters in which extractive abounds. Thus, common vinegar becomes colourless when it is boiled in pure charcoal powder; water, which has become foetid at sea, is purified by filtering it through charcoal; that intended for long voyages may be preserved perfectly pure by thoroughly charring the in sides of the casks.1

Medical properties and uses. - Charcoal is evidently an antiseptic; and, as such, has been given internally to correct the putrid eructations of some kinds of dyspepsia. But, in order that it may produce this effect, it should either be newly prepared, or such as has been preserved in very well-stopped bottles. It is probable that it operates both by correcting the foetor, and absorbing the gas generated in the stomach, as well as checking the decomposition of the undigested aliment. Dr. Calcagno, an Italian physician, proposed to employ it instead of Cinchona bark in intermit-tents2; but this suggestion has not been supported by British practitioners. It has been applied, advantageously, mixed up in powder with boiled bread, or linseed meal and water, as a poultice, to foul ulcers and gangrenous sores; and it is undoubtedly, in combination with powdered catechu, kino, or rhatany root, the best toothpowder known. I have discovered that it may be used also as a test for arsenic. (See the article Arsenic.)

The dose of charcoal may be from grs. x. to 3j. combined with rhubarb.

Officinal preparations.- Cataplasma Carbonis ligni, D. Barytae Murias, E. D.