The Typical Cellulose and the Cellulose Group 31 



The thiocarbonate reaction more especially throws light on 

 that somewhat vague quantity, the ' reacting unit ' of cellulose. 

 We use this term in preference to that of molecular weight ; for 

 the latter quantity can be determined only for bodies which 

 readily assume the simplest of states, and which can be ascer- 

 tained by physical measurements to be in that state ; whereas 

 in the case of cellulose the ordinary criteria of molecular 

 simplicity are quite inapplicable. 



We have formulated the synthesis of the thiocarbonate as 

 taking place by the interaction of C b H 10 O 5 : 2NaOH : CS 2 ; 

 or in approximate percentage ratio : 



Cellulose : Alkali : Carbon Bisulphide = 100 : 50 : 50 ; 

 or, again, in terms of the constituents estimated in the analysis 

 of the product : 



Cellulose : Alkali (Na 2 O) : Sulphur = 100 : 40 : 40. 

 If now the crude product be precipitated from aqueous 

 solution by alcohol or brine, and again dissolved and re- 

 precipitated, the ratio changes to 100 : 20 : 20 ; and, through 

 a succession of similar treatments, the ratio of alkali and 

 sulphur to cellulose continually diminishes the product, how- 

 ever, preserving its solubility. In fact, no definite break has 

 been observed in the continuous passage from the compound 

 as originally synthesised to the regenerated cellulose (hydrate). 

 It is clear, therefore, that the reacting cellulose unit is a con- 

 tinually aggregating molecule ; and if in the original synthesis 

 it appears to react as C 6 H IO O S , so in a thiocarbonate 

 containing, e.g. only 4 p.ct. Na 2 O, the unit is ioC 6 H 10 O 5 . 

 There being, moreover, no ascertainable break in the series, 

 we have no data for assigning any limiting value to the reacting 

 unit under these conditions. All we can say is, that the 

 evidence we have points to its being of indefinite magnitude ; 

 and we can see no a priori reason why it should not be so. 



In discussing this reaction we have left out of considera- 



