Adipocelluloses and Cutocelluloses 



239 



is illustrated by the following results of elementary analyses, 

 calculated in all cases on the ash-free substance (W. A. Miller, 

 Org. Chem. ed. 1869, 139-146). 



Coals. 



The coals are chemical aggregates of altogether unknown 

 constitution. By certain observations, however, they are 

 definitely connected with the earlier members of the above 

 series ; thus they yield substitution derivatives with chlorine 

 (Cross and Bevan, Chem. News, 44, 185), and yellow acid pro- 

 ducts on treatment with nitric acid, of similar composition to 

 those obtained from humic compounds, natural and artificial 

 (infra). The products of their destructive distillation (coal tar), 

 which it is needless to say have been exhaustively investigated, 

 throw, it is true, a certain light on their constitution ; but they 

 are too complex for the establishment of definite relationships 

 to the parent molecules. 



HUMIC COMPOUNDS : HUMUS. These series of compounds 



