1 8 Cellulose 



basic and ' acidic,' present in the colouring matter or mordant 

 and the substance with which it combines. 



This explanation certainly covers a wide range of such re- 

 actions, but we shall find that the molecular constitution of the 

 fibre-substance is also an important factor. This point will 

 be discussed subsequently. 



Capillary Phenomena. The absorption and trans- 

 mission of solutions by cellulose is attended by a number of 

 special effects. Schonbein appears to have been the first to 

 observe that strips of unsized paper, of which one end was 

 placed in an aqueous solution, e.g. of a metallic salt, will 

 absorb and transmit the water more rapidly than the dissolved 

 salt, which is therefore ' filtered out ' ; further, that to the 

 various salts, cellulose manifests varying degrees of re- 

 sistance to transmission in solution. These phenomena have 

 been further studied by Lloyd (Chem. News, 51, 51) for 

 metallic salts, 1 and by F. Goppelsroeder (Berl. Ber. 20, 604) for 

 various colouring matters ; the results of their observations 

 constituting the beginnings of a method of * capillary analysis 

 or separation.' The subject is comparatively new and not yet 

 systematised, but the method is undoubtedly capable of con- 

 siderable extension. 



Contrasted with the relatively feeble attractions of cotton 

 cellulose for the acids and bases of low molecular weight there are a 

 number of cases ot special combinations which take place in much 

 higher proportions. 



Thus the fibre removes a considerable quantity of barium 

 hydrate on digestion with the solution ; and from solutions of the 

 basic salts of lead, zinc, copper, tin, aluminium, iron, chromium, 

 c. the fibre takes up considerable but variable proportions of the 

 respective basic oxides. The formation of these compounds 

 underlies the well-known processes of ' mordanting' practised by 

 the dyer and printer of textiles. The theory of these processes will 



1 More recently by E. Fischer and Schmidmer, Lieb. Ann. 272, 156. 



