Preparation

By digesting the commercial charcoal with dilute hydrochloric acid for two days in a warm place; filtering, washing, drying the residue, and igniting in a closed crucible. By these processes the salts are rendered soluble, and removed as superphosphates and soluble chlorides, while carbonic acid and sulphuretted hydrogen gases are driven off.

Characters

It occurs as a smooth, black powder, which has no odor and scarcely any taste; when burned it leaves very little ash. Charcoal has certain chemical and mechanical properties which are very useful in pharmacy. That prepared from wood is used as a deoxidizing agent, as in the preparation of sulphurous from sulphuric acid (by distilling the latter with it), and the reduction of iodate to iodide of potassium. Animal charcoal is used as a decolorizer in the preparation of alkaloids, etc. Its power in this respect is such that diluted tincture of litmus will filter through it colorless. Warrington ascertained that it would remove the bitterness of hops and other vegetable infusions, and Dr. Garrod soon afterward pointed out that it would destroy the activity of many organic poisons, as opium, aconite, and nux vomica (Lancet, ii., 1845). Animal charcoal is much more powerful as an antidote than that prepared from wood.

Both varieties possess great absorptive power, taking up more than twice their weight of gases, and may be used for purifying water by filtration, and for the disinfection of sewer-emanations, and the deodorizing of sick-rooms, dissecting-rooms, etc. (Letheby). A respirator containing a layer of charcoal has been recommended (Stenhouse, Marcet).

Preparations And Dose

Of wood charcoal, many varieties are in use, some practitioners giving the preference to that made from heavy woods (box, acacia, etc.), others to the light woods (poplar or willow). Dr. A. Leared recommended that made from "vegetable ivory." Charcoal from the haematoxylon campechianum is good, but has been overpraised. Belloc's is also a good preparation; it is made from poplar. Biscuits and lozenges of charcoal are also used, but in my experience are not so effective as the powder, and they sometimes irritate the stomach. Carbo ligni: dose, as antacid, antiseptic, or absorbent, 10 to 60 gr., or more. Cataplasma carbonis ("charcoal poultice") contains 1/2 oz. of wood charcoal. Carbo animalis is to be preferred as an antidote to poisons: dose, from 1/2 oz. to 2 oz. or more, according to the amount of poison swallowed; it is best taken suspended in water. Carbo animalis purifcatus: dose, 20 to 60 gr. or more.

[Preparations, U. S. P. - Carbo animalis, Carbo animalis purificatus, and Carbo ligni.]

Therapeutical Action (External)