320 DECOMPOSITION OF WOOD, COAL, ETC. 



Wood C36 H22 O22 



To this add 5 atoms of water , . . H 5 O 5 



3 atoms of oxygen .... O 3 



C36 H27 O30 

 Subtract from this 3 atoms Carbonic acid C 3 O 6 



C33 H27 O24 



The process of mouldering is, therefore, one of 

 putrefaction and decay, proceeding simultaneously, 

 in which the oxygen of the air and the component 

 parts of water take part. But the composition of 

 mouldered wood must change according as the 

 access of oxygen is more or less prevented. White 

 mouldered beech-wood yielded on analysis 47'67 

 carbon, 5*67 hydrogen, and 46*68 oxygen ; this 

 corresponds to the formula C33 H25 O24. 



The decomposition of wood assumes, therefore, 

 two different forms, according as the access of the 

 air is free or restrained. In both cases carbonic acid 

 is generated; and in the latter case, a certain 

 quantity of water enters into chemical combination. 



It is highly probable that in this putrefactive 

 process, as well as in all others, the oxygen of the 

 water assists in the formation of the carbonic acid. 



Wood coal (brown coal of Werner) must have 

 been produced by a process of decomposition 

 similar to that of mouldering. But it is not easy to 

 obtain wood coal suited for analysis, for it is gene- 

 rally impregnated with resinous or earthy sub- 

 stances, by which the composition of those parts 

 which have been formed from woody fibre is essen- 

 tially changed. 



