7M PRELIMINARY OBSERVATIONS. 



any change of the volume of the gas ; but while dry sawdust 

 lost three parts by weight of carbon in this way, it diminished 

 in weight by fifteen parts altogether, shewing that twelve parts 

 of water were at the same time separated from the wood. Hence 

 the proportion of carbon in decaying wood increases with the 

 progress of its decay ; and it is concluded that the hydrogen 

 only is oxidised at the expense of the oxygen of the air, while 

 the carbonic acid is formed from the elements of the wood 

 (Liebig). The composition of pure woody fibre or lignin being 

 ^36^22^)22? two different specimens of mouldered oak wood, 

 (the humus from oak wood) were found to be C 35 H' 20 O 20 and 

 C34H 18 O 18 , or for every two atoms of hydrogen oxidised by the 

 air, one atom of carbonic acid (CO 2 ) has been formed at the 

 same time from the elements of the wood and set free. When 

 water is present and the access of air restrained, the decompo- 

 sition of wood appears to proceed in a different manner; for 

 while carbonic acid is generated as before, a certain quantity of 

 water enters into chemical combination, white mouldering beech - 

 wood being found to have a composition corresponding with 

 the formula C 33 H 25 O 24 . There is reason, however, to suppose 

 the interference in such cases of mouldering, of a species of 

 fermentation such as was observed when rags were placed in 

 heaps and wetted in the preparation of a substance for the fa- 

 brication of paper, according to the old process in use before 

 the application of chlorine. The rags became warm and dis- 

 engaged a gas, while their weight diminished from 1 8 to 25 per 

 cent. It is probable that in this, as well as other putrefactive 

 processes, the oxygen of the water assists in the formation of 

 carbonic acid. 



Wood coal or brown coal, which retains the structure of 

 the wood unchanged, appears to be produced by a similar 

 process of decomposition. A specimen free from bituminous 

 matter was found to have a composition expressed by the 

 formula C 33 H 21 O 16 ; and may therefore have been produced 

 from woody fibre by the separation of one equivalent of hydrogen 

 and three equivalents of carbonic acid. In all varieties of wood 

 coal, the proportion of oxygen in relation to the hydrogen is 

 diminished, these elements existing in the original woody fibre 

 in the same proportion as in water, indicating a disengagement 

 of carbonic acid from their substance, which appears still to go 



