The Typical Cellulose and the Cellulose Group 5 



OH groups in the cellulose molecule, for in proportion as 

 these are suppressed by combination (with negative radicles to 

 form the cellulose esters) the products exhibit decreasing 

 attractions for atmospheric moisture. It is to be noted that 

 some of these synthetical derivatives are formed with only 

 slight modifications of the external or visible structure of the 

 cellulose, of which, therefore, the phenomenon in question is 

 again shown to be independent. 



(3) The 'condition* of the fibre-substance in respect of 

 hygroscopic moisture is an important factor of such properties 

 of fibre as make up its spinning qualities ; it also seriously 

 affects the tensile strength of papers and cellulose textiles. 



(4) A study of the hydration and dehydration phenomena 

 of the celluloses indicates an unbroken continuity in the series 

 of cellulose-water compounds or cellulose hydrates ; of which 

 series the * water of condition ' or hygroscopic moisture of a 

 cellulose represents the final terms. 



The proportion of water held by the celluloses in an atmosphere 

 saturated with aqueous vapour is necessarily very much greater 

 than in the ordinary atmosphere, partially saturated at the same 

 temperature. (See H. Miiller, Pflanzenfaser, p. 3.) 



The * moisture of condition ' is a factor of some moment, first in 

 the buying and selling of fibrous products, and secondly in the 

 processes by which they are worked up (spinning, and 'finishing'). 



(1) In a delivery of ico/. value of a fibrous material, e.g. 

 paper pulp or half stuff, the ordinary variations in the atmospheric 

 moisture may occasion a difference of I/, to 2.1. in the value. It is 

 important, therefore, to have a normal standard of reference. In 

 the case of wood pulp or cellulose in which there is a large com- 

 merce it is customary to fix this at 10 p.ct., which means that 100 

 of air-dry pulp give 90 'dry' at 100 C. 



If, therefore, in any test the percentage of dry pulp is estimated 

 at any figure, the corresponding percentage of 'normal' air-dry pulp 

 (10 p.ct. Aq) is obtained by adding -*- to the percentage of dry pulp. 



(2) Cotton-spinning is carried on under special and carefully 

 regulated conditions of temperature and atmospheric moisture, 



