6 Cellulose 



which have been arrived at as the result of accumulated observa- 

 tion and experience. Raw cotton, however, is not by any means 

 a pure cellulose, and the spinning properties of the fibre are to a 

 certain extent conferred by the substances associated, in admixture 

 or combination, with the cellulose. There is no doubt, however, 

 that the physical properties of the cellulose are largely modified 

 by its water of condition ; and the fine adjustments of these ulti- 

 mate fibres to the conditions of the spinning frame, more espe- 

 cially in regard to the drawing and twisting, largely depend upon 

 the maintenance of an * optimum ' of hydration of the cellulose. 



(3) Finishing processes textiles and paper. The * finish ' of 

 textiles and papers for the market is of very various kinds. The 

 last operations are those of closing and * surfacing,' and consist of 

 the mechanical treatments of beetling, mangling (textiles), calen- 

 dering, and glazing (textiles and paper). 



The finish is considerably affected by the condition of hydra- 

 tion of the fibre, and this is affected by the method of drying up 

 (air-drying or hot-drying) and the amount of moisture present in 

 the fibre when submitted to the mechanical treatments. The 

 operation of causes of this kind is necessarily somewhat obscure. 

 The student should address himself to the work of observation of 

 the phenomena of hydration of the celluloses, studying all the 

 conditions which affect, and the changes which accompany, the 

 loss and gain of water. 



It is evident from a very superficial examination of the plant 

 world that the celluloses originate in the gelatinous form, i.e. in 

 a condition of extreme hydration. Hydrates of identical cha- 

 racteristics are obtained on precipitating cellulose from solutions 

 in the several special solvents to be subsequently described. 

 These hydrates differ in certain respects from the anhydrous or 

 dehydrated celluloses ; thus they dissolve in strong nitric acid, 

 and in solutions of the alkaline hydrates of moderate concen- 

 tration, they also are more readily attacked (hydrolysed) by 

 boiling dilute acids and alkalis. It is necessary to keep this 

 in view in regard to the determination of cellulose in fresh 

 tissues. A previous dehydration of the tissue by air-drying or 



