26 Cellulose 



the further hydration of the compound allowed to proceed 

 spontaneously some hours (e.g. over night). On stirring, a 

 homogeneous liquid is obtained, which may be diluted to any 

 required degree. 



Thus prepared, the crude solution is of a yellow colour, due 

 to by-products of the reaction (trithiocarbonates). The pure 

 compound is obtained either by treatment of the solution with 

 saturated brine or with alcohol. It forms a greenish-white 

 flocculent mass or coagulum, which redissolves in water to a 

 colourless or faintly yellow coloured solution. Solutions of 

 the salts of the heavy metals added to this solution precipitate 

 the corresponding xanthates. Iodine acts according to the 

 typical equation : 



CS + CS + ' = * NaI + CS ' 



SNa 



The compound, which may be described as a cellulose 

 dioxythiocarbonate, is precipitated in the flocculent form ; it 

 is redissolved by alkaline solution, in presence of reducing 

 agents, to form the original compound. 



The most characteristic property of the cellulose xanthates is 

 (a) their spontaneous decomposition into cellulose (hydrate), alkali, 

 and carbon disulphide or products of interaction of the latter. 

 When this decomposition proceeds in aqueous solution, at any 

 degree of concentration exceeding i p.ct. cellulose, a jelly or 

 coagulum is produced, of the volume of the containing vessel. 

 These highly hydrated modifications of cellulose lose water 

 very gradually, the shrinkage of the ' solid ' taking place sym- 

 metrically. The following observations upon a 5 p.ct. solution 

 (cellulose), kept at the ordinary atmospheric temperature, will 

 convey a general idea of the phenomena attending the regene- 

 ration of cellulose from the alkali xanthate. The observations 

 were made upon the solution kept in a stoppered cylinder ; 

 after coagulation the solution, expressed from the coagulum of 



