358 CARBON. 



are more easily absorbed than gases, and liquids more easily still. It 

 evidently depends upon the porous form of the charcoal, and plum- 

 bago does not possess it at all. The power seems to be analagous 

 to that of capillary attraction in other solids. When oxygen is ab- 

 sorbed, carbonic acid is formed at the end of several months ; if char- 

 coal is impregnated with sulphuretted hydrogen, and exposed to the air 

 or to oxygen gas, sulphur is evolved, and water formed, the gas 

 being destroyed, and considerable heat produced, so as, in some 

 cases, to produce in a few minutes, detonation with oxygen gas, and 

 more or less heat is always evolved when gases are absorbed by char- 

 coal.* In general after 24 hours, the absorption is not increased, ex- 

 cept in the case of oxygen gas, which goes on absorbing for years, 

 in consequence of the formation of carbonic acid. The gas is easily 

 extracted by the air pump, and during its extrication, cold is pro- 

 duced. Charcoal which has absorbed a gas will give it out en- 

 tirely by being heated again, and very strikingly with ebullition, by 

 plunging it into boiling hot water. The charcoal can be as effect- 

 ually prepared for absorbing gases by the air pump as by ignition. f 

 This property is common more or less to all porous bodies ; asbes- 

 tos, silk, meerschaum, adhesive slate, agaric mineral, wool, linen 

 thread, plaster of Paris solidified by water, &c. have been made sub- 

 jects of similar experiments. { 



(g.) By exposure to the air, charcoal increases in weight, by ab- 

 sorption of water, air, &c., f of which is water. By a week's ex- 

 posure, lignum vita3 gained 9.6 per cent., fir 12.0, box 14.0, beech 

 16.3, oak 16.5, mahogany 18.0. Allen and Pepys. 



(h.) Infusible by any heat which we can apply, except that of gal- 

 vanism. \\ 



(i.) Insoluble in water, although at a red heat, it decomposes that 

 fluid, (vide carburetted hydrogen.) 



* Proportioned to the rapidity and amount of absorption ; 25 in the case of car- 

 bonic acid. 



t Quere Whether also for conducting- galvanism, and for antiseptic agency ? 



\ Turner, 2d Ed. p. 235, and Vasel,in Sweigger's Jour. 



Charcoal absorbs from air more oxygen than nitrogen ; when recently ignited 

 and confined in air, over mercury, it left only 8 per cent. ; and if from a state of 

 full ignition, it be plunged into water, and then confined in air over mercury, the 

 oxygen is nearly or quite all absorbed, leaving, as is said, pure nitrogen. We are not 

 informed whether the pure oxygen can be recovered by heating the charcoal. 



|| Fusion of char codify the use of Dr. Hare's Deflagrator. The poles being ter- 

 minated by well prepared charcoal, a knob of fused matter appears on the copper or 

 negative pole, sometimes half an inch in length, while a cavity, corresponding in 

 position, appears on the zinc or positive pole, and if the pieces are made to change 

 places, the knob and cavity are transferred from side to side. The knob appears 

 to come from the opposite pole, and is evidently derived from the charcoal. It is 

 very difficult to burn, but if heated either in oxygen gas by the sun's rays, or 

 in common air, or mixed with nitrate or chlorate of potash, it produces carbonic 

 acid. On an ignited iron in the air, it wastes slowly away. It is smooth and glis- 

 tening, with semi-metallic hues; its color gray, or almost black; not fibrous or 



