338 Cellulose 



work, a resume* of important recent investigations of Vieille and 

 Mendeljeff. 



Cellulose Sulpho-carbonates (Viscose). The authors have 

 published an account of later researches into the nature and con- 

 stitution of this series of compounds. The main point established 

 is that the affinity of the cellulose xanthogenic acid is consider- 

 ably higher than that of the fatty acids, and generally higher than 

 that of the monocarboxylic acids. Consequently the solutions of 

 the crude compound may be treated e.g. with acetic acid in 

 excess without decomposing the alkali salts of the cellulose 

 sulphocarbonic acid. The acetic acid, on the other hand, entirely 

 decomposes the by-products of the original reaction and reactions 

 of spontaneous decomposition. By this means the isolation of pure 

 compounds of this series is much facilitated, the separation from 

 sodium acetate on addition of alcohol being satisfactorily sharp. 



The following stages in the process of reverse decomposition 



, 



have been established : The general formula C S\ having 



X SNa 



been verified with satisfactory precision, and X being the cellulose 

 residue of various dimensions, it is found that when freshly pre- 

 pared X lies between C 6 and C ]2 , and the compound is not 

 precipitated by dehydrating agents : as X approaches C ]2 the 

 xanthate is precipitated by alcohol, and readily redissolves in 

 water : the C 24 xanthate is precipitated by smaller proportions of 

 dehydrating agents from alkaline solutions, and is entirely pre- 

 cipitated by acetic acid ; in other words, is insoluble in water. The 

 cellulose when reaggregated to these dimensions is not soluble as 

 a sodium xanthate, but requires the further combination of its 

 OH groups with the alkaline hydrate to produce a soluble com- 

 pound. These stages are well defined, and by their general 

 recurrence in the course of investigations to the apparent exclusion 

 of intermediate stages, it is suggested, though it cannot be finally 

 affirmed, that the decomposition as it actually occurs in the solu- 

 tion takes place in the later stages by units of C 12 dimensions. 



The analysis of viscose solutions is obviously much simplified 

 by these observations. By volumetric estimation, using succes- 

 sively normal acetic and hydrochloric acids, the alkali combined 

 with the cellulose is determined, and the number can be confirmed 

 by titration with a standard iodine solution. (Berl. Ber., 1901, 

 34, 1513-20.) 



