i)r. BoUey on the Theory of Dyeing. 505 



Esprit*, Schonbeinf, GutlieJ, Stenl]ouse§, notwithstauding 

 many clifFereuces ou isolated points, certain concordant results: 



1. That the same charcoal produces a greater effect on one 

 solution than on another. 



2. That charcoals of different origin and preparation may pro- 

 duce very different effects. 



3. That charcoal takes up some salts from their solutions un- 

 changed, but that it decomposes others, either attracting the base 

 more strongly and leaving an acid or an acid salt, or reducing 

 the base to a lower degree of oxidation. 



The reduction of bases by fibres immersed in solutions of me- 

 tallic salts has not, as far as we know, been observed ; but the 

 decomposition of a neutral into an acid and a basic compound 

 occurs several times in the above Table of experiments. In this 

 respect also the behaviour of the fibres is therefore very similar 

 to that of charcoal. 



Putting together the conclusions which may be deduced, 

 partly from the observations cited, partly from general consi- 

 derations, we may regard it as proved : — 



A. With regard to the part of the fibre in which the colouring 

 matter is deposited. 



1. The penetration of the fibres by the colouring matter is 

 not so general as Verdeil and Oschatz suppose ; and the external 

 adhesion of the dye cannot be regarded as an exception. 



2. The view of Persoz, that the colour of dyed fibre is due 

 soleli/ to superficial adhesion, is as little to be maintained. 



3. Silk and avooI, in all cases where they have not been dyed 

 with colours in a mere state of suspension, seem to be impreg- 

 nated with the dye throughout their entire mass. 



4. Both these kinds of fibre, but especially the first (silk), are 

 in many cases coloured, not only internally, but also by external 

 adhesion. 



5. In the case of cotton, the penetration of the cell-walls by 

 the dye is often wanting ; and when it occurs, it is generally only 

 slight. By far the larger portion of colouiing matter adheres to 

 the surface of the fibre. 



6. W. Crumbs view, that in cotton fibres there are two parallel 

 canals which contain the greater part of the colouring matter, is 

 unfounded. In particular cases, however, the colouring matter 

 does penetrate into and partly fill the internal space of the 

 fibre. 



* Journal de Pharmacie, S. 3. vol. xvi. i)p. 192 and 264. 

 t PoggendorfF's Annalen, vol. Ixxviii. p. 521. 

 X Arcliiv der Pharmacie, S. 2. vol. Ixix. p. 121. 

 § Annalen der Chernie, vol. ci. p. 213. 



