The Typical Cellulose and the Cellulose Group 33 



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concentration of the alkaline solution. The fibrous benzoate 

 produced under these conditions shows necessarily a much 

 increased volume ; examined microscopically the features of 

 minute structure of the fibre are seen to be much accentuated. 

 The hygroscopic moisture of the product is 2-3 p.ct. of its 

 weight, i.e. from to \ that of the original cellulose. This 

 weakened attraction for atmospheric moisture invariably 

 attends the substitution of the OH groups in the celluloses 

 by acid residues. 



(b] Soluble alkali celluloses. The hydrates precipitated 

 from solution in the zinc chloride and cuprammonium solu- 

 tions dissolve in solutions of the alkaline hydrates ; and the 

 benzoates obtained from these solutions, by treatment with 

 benzoyl chloride, are curdy precipitates, which may be purified 

 by solution in glacial acetic acid, filtering, and reprecipitating 

 by water. Obtained in this way, the benzoates approximate 



in composition to C 6 H 8 O 3 <Q' 7 [^Q. They melt at a high 



temperature to a clear liquid, which solidifies to a transparent 

 resinous mass. By friction the compound becomes highly 

 electric, a property common to the esters of cellulose. 



The compound dissolves in acetic anhydride ; on heat- 

 ing for some time at the boiling-point of the liquid, a partial 

 replacement of the benzoyl by acetyl groups occurs, and at 

 the same time a further acetylation of the cellulose. 



The compound gives, on analysis, numbers corresponding 

 with the empirical formula, 



C 6 H 6 O.O.C 7 H 6 0.(O.C 2 H 3 0) 3 . 



This group of benzoates and mixed esters requires further 

 and exhaustive investigation, as a study of their composition 

 and constitution cannot fail to throw much light upon that of 

 the parent molecule. 



We now leave the alkali celluloses, and the synthetical 



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