('AUIJON AND THi; II YI>li< H'A I!H< >NS 331 



place in the shape of a black, infusible, non-volatile charcoal familiar 

 to all. The earthy matter and all non-volatile substances (ash) form- 

 ing a part of the organic matter, remain behind with the charcoal. The 

 tar-like substances, which require a high temperature in order to de- 

 compose them, also remain mixed with charcoal. If a volatile organic 

 substance, such as a gaseous compound containing oxygen and hydro- 

 gen, be taken, the carbon separates on passing the vapour through a 



form water, but also to unite with the carbon to form carbonic anhydride. The 

 greater part of vegetable tissue consists of the cellulose, C 6 H 10 O 5 ; from its composi- 

 tion it is i-vidt'iit that the oxygen is insufficient to transform the hydrogen into water and 

 the carbon into carbonic anhydride, because for this purpose it would require 17 

 quivalents and it only contains 5. This reasoning also refers to all the remaining 

 organic substances. Under the action of air, organic substances are capable of oxidising 

 to such an extent that all the carbon and all the hydrogen they contain will be trans- 

 formed into carbonic anhydride and water. The refuse of plants and animals are subjected 

 to such a change whether they slowly decompose and putrefy, or rapidly burn, with direct 

 access to air. But if the supply of air be limited, then, in virtue of the above-stated 

 reasoning, there can be no complete transformation into water and carbonic anhydride, 

 and therefore, if organic matter decomposes under these conditions, charcoal must 

 remain, as it is a non-volatile substance. All organic substances are unstable, they do 

 not resist heat, and in time easily change at ordinary temperatures, particularly if water 

 be present. Therefore it is easy to understand that charcoal may be obtained in many 

 cases through the transformation of substances entering into the composition of 

 organisms, but that it is never found in a pure state. 



The transformation of organic matter is not, however, so simple as would appear 

 from the preceding statements ; that is to say, water and carbonic anhydride are not the 

 only products separated from organic substances. Carbon, hydrogen, and oxygen are 

 capable of giving a multitude of compounds ; some of these are volatile compounds, 

 gaseous, soluble in water they are carried off from organic matter, undergoing change 

 without access of air. Others, on the contrary, are non-volatile, rich in carbon, constant 

 under the influence of heat and other agents. The latter remain in admixture with 

 charcoal where the decomposition takes place; such, for example, are tarry sub- 

 stances. The quantity of those bodies which are found mixed with the charcoal is very 

 varied, and depends on the energy and duration of the decomposing influence. For 

 instance, when wood is first acted on by heat, the moisture separates ; it then turns 

 brown, but still contains a large amount of oxygen and hydrogen. If the action be 

 further continued the quantity of these latter elements diminishes, and the proportion of 

 carbon in the residue increases, although a part of it is carried off in the shape of the 

 volatile products of decomposition. The greater the heat, the less the quantity of char- 

 < oal obtained, and the less the amount of hydrogen and oxygen contained in the remain- 

 ing charcoal. The annexed table shows, according to the data of Violette, those changes 

 to which wood is subjected at various temperatures when submitted to dry distillation by 

 nu'ansof superheated steam: 



Residue 



Temperature from 100 parts In 100 parts of the residual charcoal 



of alder wood 



C H andN A>h 



150 lOO'O 47'5 <)! 46'8 O'l 



850 29'7 76-6 4'1 18'4 0'6 



1082 18'7 Hl-i) 2-8 14-1 1'6 



l :,oo 



17-8 95-0 0-7 :!-s T7 



