Experimental and Applied 295 



1 chemical,' process. As, however, the ' constants of solution,' 

 i.e. the properties of bodies in solution, are now definitely corre- 

 lated with molecular weight, the distinctions obviously vanish 

 in this case, and the corresponding terms are absorbed in that 

 of more comprehensive significance viz. ' molecular.' So also 

 it may fairly be stated in connection with the phenomena of 

 dyeing. If solution is defined as the homogeneous distribution 

 of one substance through the mass of another regarded as the 

 solvent, the dyeing process is a special case of transference of a 

 body from one solvent to another, and a dyed fibre is a solid 

 solution of the colouring matter in the fibre-substance. The 

 conditions determining the transfer, in the process, from water 

 to fibre-substance are certainly complex : they depend (i)upon 

 the constitutional relationships of fibre-substance and colouring 

 matter ; (2) upon osmosis and all those conditions by which it 

 is influenced. 



In regard to the first and chief factor, a very superficial 

 view of dyeing processes points to the important influence of 

 the chemical properties of the fibre-substance. But, in 

 extending this view to a detailed discussion, we are met at once 

 by the great disparity between these two groups of carbon 

 compounds, i.e. fibre-substances and colouring matters, in 

 their relationship to the science. The latter are, as a class, 

 bodies of the most definitely ascertained constitution, and are 

 synthesised, in many cases, by * quantitative' reactions from their 

 constituent groups ; whereas the constitution of the former is 

 still highly problematical in every direction. A comprehensive 

 view of dyeing phenomena is necessarily, therefore, deferred 

 until the latter group shall have been more fully investigated. 

 At the same time, we have positive knowledge of the reactive 

 groups of the fibre-substances, sufficient to indicate the part 

 which they play in dyeing phenomena; and these reactions 

 have already been discussed, in the case of the celluloses, as a 



