Experimental and Applied 299 



reaction in their property of taking up the blue cyanides from 

 solutions of ferric ferricyanide. It is not a question here of a 

 merely superficial oxidation of the fibre-substance by the ferri- 

 cyanide, and a staining of the fibre with the resulting blue 

 cyanide. From the detailed description previously given (p. 1 24) 

 it is seen to be a specific reaction between the fibre-substance 

 and the ferricyanide, taking place in altogether unique quan- 

 titative proportions. It does not depend upon any anterior 

 reduction by the fibre-substance, as it is unaffected by the 

 presence of powerful oxidising agents ; nor upon the relation- 

 ships to the fibre-substance of either ferric oxide or hydroferri- 

 cyanic acid, since in any other form of combination they exert 

 but slight action. From the evidence, it appears probable that 

 the Hgnocellulose takes up the ferric ferricyanide as a whole, in 

 the first instance such combination having rather the features 

 of a ' physical ' reaction and then redistributes its constituent 

 groups in such a way that the ferric oxide is deoxidised with 

 formation of the blue ferroso-ferric cyanide. In this second 

 effect the constitution of the characteristic groups of the ligno- 

 cellulose is the active cause. 



These two reactions or groups of dyeing phenomena have 

 been instanced, not only because they are of critical and unique 

 value as test-problems for any theory of dyeing, but as further 

 illustrating the varied aspects of the subject of cellulose 

 chemistry. With progress in the theory of dyeing, it is highly 

 probable that the effects themselves may come to be available 

 as criteria of constitution of the fibre-substances ; in the mean 

 time it is equally probable that further elucidation of these 

 problems in other directions may contribute materially to the 

 establishment of a theory more generally acceptable than the 

 much controverted views at present held. 



In the processes of printing the vegetable textile fabrics the 

 same general considerations obtain. The treatments are, how- 



