The Typical Cellulose and the Cellulose Group 79 



(b) Those of lesser resistance to hydrolytic action, arid con- 

 taining active CO groups. 



(c) Those of low resistance to hydrolysis, i.e. more or less 

 soluble in alkaline solutions and easily resolved by acids, with 

 formation of carbohydrates of low molecular weight. 



Group (a). In addition to the typical cotton cellulose 

 which, it is to be noted, is a seed-hair there may be included 

 in this group the following fibrous celluloses which constitute 

 the bast of exogenous flowering annuals : viz. the celluloses of 

 Flax (Linum usit), Hemp (Cannabis sativa), China Grass 

 (Rhea and Boehmeria species) ; and of the lesser known 

 Marsdenia tenacissima, Calotropis (gigantea), Sunn Hemp 

 (Crotalaria juncea). 



As in the case of cotton, the celluloses of the fibres are con- 

 sidered in the form of the white (or bleached) and purified 

 residues resulting from the treatment of the raw materials by 

 processes of alkaline hydrolysis and oxidation more or less 

 severe in character. For the purification of the celluloses in 

 the laboratory the methods usually practised consist in (i) 

 alkaline hydrolysis, i.e. treatment with boiling solutions of 

 sodium hydrate, carbonate, or sulphite ; (2) exposure to bro- 

 mine water or chlorine gas ; or when oxidation alone is suffi- 

 cient for the removal of the * impurities,' to solutions of the 

 hypochlorites or permanganates (in the latter case followed by 

 a treatment with sulphurous acid to remove the MnO 2 de- 

 posited on the fibre-substance) ; (3) repetition of (i) for the 

 removal of products rendered soluble by (2). 



Special accounts of these raw fibrous materials are contained 

 in Spon's 'Encyclopaedia Industrial Arts'; 'Die Pflanzenfaser,' 

 Hugo Miiller (A. W. Hofmann's ' Bericht.' Braunschweig, 1877); 

 1 Report on Indian Fibres and Fibrous Substances,' Cross, Bevan, 

 and King (Spon, London, 1887) ; and ' Chemische Technologic d. 

 Gespinnstfasern,' O. N. Witt (Braunschweig, 1888). 



