322 



Cellulose 



to a series of index numbers which express the property con- 

 versely in regard to the diffusible substances ; thus a given 

 substance is characterised by the index number, which is the 

 strength of alcohol required to produce a membrane which just 

 prevents diffusion of the substance. The'Jollowing is a table 

 of such index numbers : 



This investigation is of moment as a definite adumbration 

 of interior cellulose structure, and the actual mechanism of the 

 osmotic exchanges in relation thereto. The extension of the 

 author's methods to derivatives and other forms of cellulose 

 cannot fail to lead to positive conceptions of the actual con- 

 dition of cellulose matter. 



In connection with this subject we note a paper by P. A. 

 Kober (J. Amer. Chem. Soc. (1917), 39-944), on { Per- 

 vaporation ' and related phenomena. It is found that water held 

 in a container of nitro- cellulose (film), and of other colloids, 

 evaporates through the walls of the container as though no 

 membrane were present. The observation has been applied 

 in various directions : thus, for the concentration of sterilised 

 solutions without infection. ' Percrystallisation ' of dialysable 

 substances occurs on the outer surface of membranes when a 

 solution is thus concentrated to saturation in respect of that 

 constituent. 



In this connection we must also notice a paper on ' The 

 Absorption of Gases by Celluloid,' by V. Lefebure (J. Chem. Soc. 

 (1914), 105, 328), in which are recorded observations on carbonic 

 anhydride, the air gases and hydrogen in regard to absorption 



