The Typical Cellulose and the Cellulose Group 25 



cavity of the cell wall. Owing to this thickening the cavity of 

 die cell is almost obliterated. Another effect of the alkali is to 

 produce a peculiar spiral twisting of the fibre, which further 

 explains the shrinkage of cloth in the process of mercerising ; the 

 shrinkage being in part due to the felting together of the twisted 

 fibres, after the manner of wool fibres in the process of 'fulling 'cloth. 



CELLULOSE THIOCARBONATES. When 'mercerised' cot- 

 ton, or more generally an alkali-cellulose (hydrate), is exposed 

 to the action of carbon disulphide at the ordinary temperature, 

 a simple synthesis takes place, which may be formulated by the 

 typical equation : 



X.ONa + CS 2 = CS. *. 



The best conditions for the reaction appear to be when the 

 reagents are brought together in the molecular proportions : 



C 6 H, f5 .NaOH CS, 



the second ONa group being in direct union with the cellu- 

 lose molecule, which reacts, therefore, as an alkali cellulose. 

 The resulting compound may therefore be described as an 

 alkali-cellulose-xanthate. It is perfectly soluble in water, to a 

 solution of extraordinary viscosity. The course of the reaction 

 by which it is produced is marked by the further swelling of 

 the mercerised fibre and a gradual conversion into a gelatin 

 ous transparent mass, which dissolves to a homogeneous solu- 

 tion on treatment with water. 



To carry out the reaction in practice, bleached cotton is 

 treated with excess of a 15 p.ct. solution of NaOH, and 

 squeezed till it retains about three times its weight of the solu- 

 tion It is then placed in a stoppered bottle with carbon 

 disulphide, the quantity being about 40 p.ct. of the weight 

 of the cotton. After standing about three hours at ordinary 

 temperatures, water is added sufficient to cover the mass, and 



