MANUFACTURE OF CHARCOAL. 131 



Charcoal -u-ill absorb coloring matter, forming insoluble compounds 

 with many inorganic bodies. It is probable that the bodies absorbed 

 contract a kind of adhesion upon the surface, in the manner of mordants 

 in fixing the colors in tissues. The organic matters absorbed cannot be 

 separated without modifications; wood-charcoal absorbs gases without 

 combining with them. The volume is variable according to the nature 

 of the gas, those most soluble in water being most absorbed by the 

 charcoal. The volumes of different gases absorbed are stated as follows : 

 for one of charcoal, viz, ammonia, 90; hydrochloric acid, 85; sulphuric 

 acid, 65; hydro-sulphuric acid, 55; protoxide of nitrogen, 40 ; carbonic 

 acid, 35; bicarbonated hydrogen, 35; oxide of carbon, 9.42; oxygen, 

 9.25; nitrogen, 7.5; hydrogen, 1.75. Gases absorbed by charcoal are 

 given out in a vacuum. Damp charcoal loses in a great degree its 

 property of absorbing gases. 



In the industries this absorbing power of charcoal is employed in dis- 

 infecting certain places where noxious gases abound, and in purifying 

 liquids. Muddy waters filtered through charcoal placed in layers be- 

 tween sand will be rendered pure and potable, and may be preserved 

 a long time. The inside of water-casks in ships, if charred, will keep 

 the waters sweet for a long time. 



Charcoals made from certain vegetable substances are employed as 

 coloring substances, such as Spanish black from cork, peach-black from 

 peach-stones, and lampblack from resinous woods and the resins. 



The Chinese have a method of charring wood in pits and arched cham- 

 bers in the ground, and carry the process to great perfection.^ 



The Moreau process. — Attention has been drawn in France within a 

 few years to a process of carbonization invented by Jules Moreau, by 

 which it is claimed a saving is made in the amount and quality of the 

 charcoal, and still further in the condensation of volatile products, by 

 which the oflensive odors of coal-making are avoided, and profitable 

 materials besides charcoal are obtained. 



This apparatus consists of a cylinder of thick sheet-iron, of a size 

 that can be easily carried by two men, about two meters high, and of 

 the same diameter. It will hold about six cubic meters of wood and 

 has at the upper end a manhole for filling with wood, and a pipe 

 through which the fire is introduced in kindling and the smoke may 

 escape. At the lower part are six registers through which the air is 

 admitted into a circuLar tube pierced with holes on the under side, so 

 that the air is sifted, as it were, in entering the vessel. The apparatus 

 sets on the ground, and has no bottom, so that when the operation is 

 finished it can be turned over on its side and the charcoal is at once 

 obtained. The yield is claimed to be from 41 to 43 per cent, in value, 

 and 30 per cent, in weight, a hectoliter of such coal weighing 23 to 25 

 kilograms. It is also used for carbonizing peat. The quality of the 

 coal may be varied, and wood may be torrified for use in high furnaces, 

 the yield in this case being 75 per cent, volume. Three workmen can 

 tend ten pieces of this ai>paratus, each yielding 25 hectoliters of char- 

 coal.2 



The Dromart jprocess.— This consists in carbonizing wood in an appa- 

 ratus made of iron, which may be taken apart in sections and put up in 

 a new phice, as occasion may require. It allows the process of carbon- 

 ization to be regulated so that it may be done rapidly or slowly, and, as 



'See Percy's Metallurgy (1875), p. 384, where figures are given of the constructions 

 used. The Aimuaire du Jour, des Mines de Bussie, 1838, p. 375, gives an article, by M. 

 Kovanko, describing the Chinese methods. 



* lievuc des Eaux et Forets, vi, 94 ; viii, 416 ; xi, 366. 



