52 Cellulose 



alcoholic function ; and (3) that with the breaking down of the 

 molecule, OH groups of the cellulose units are brought into 

 play with acid functions. 



It will be noted that up to this point we have been dealing 

 with compounds of cellulose products obtained by synthetical 

 reactions with acid and basic groups and with salts ; in all of 

 which the reacting molecule is maintained at or near its 

 maximum weight (magnitude). We have mentioned incident- 

 ally, on the other hand, that the cellulose molecule, in the sense 

 of the reacting unit, is a variable quantity ; and that, while 

 under certain conditions the tendencies are towards aggregation 

 (thiocarbonate reaction), under others the tendency is towards a 

 progressive disintegration. This is notably the case in the reac- 

 tion with sulphuric acid just described, in which there is a per- 

 fectly graduated transition from the complex colloid molecule 

 to the simple dextrose unit, a crystallisable solid of low molecular 

 weight. These considerations lead up to the study of the 



Decompositions of cellulose, which we shall find group 

 themselves under the headings 



(a) Decompositions determined by the non-oxidising acids 

 the changes resulting from addition or subtraction of H 2 O. 



(b) Decomposition by oxidants, with attendant or second- 

 ary effects of hydrolysis and condensation. 



(c) Decompositions by ferments ; (d) by heat 



None of these decompositions of cellulose are of a simple 

 character. Any aggregate change of composition can, of course, 

 always be determined ; as, however, we have no knowledge of 

 the molecular magnitude and configuration, either of the parent 

 molecule or of its derivatives i.e. such as preserve the general 

 characteristics of the celluloses* we are limited to the statistical 

 study of these reactions, together with general inferences based 

 upon their particular character. 



