624 REPORT— 1903. 



clear that under sucli conditions it is absolutely impossible to ascertain, even with 

 a small degree of accuracy, the amount of colour which has been actually taken 

 up by the fibre. 



The author considers himself justified in stating that these two fundamental 

 supports upon which the chemical theory of dyeing rests cannot withstand any 

 searching criticism. 



A considerable number of facts have accumulated during recent years which 

 tend to strengthen the view that the processes of dyeing are uniform and of a 

 mechanical nature. The author showed in 1894 that, in dyeing silk with indigo- 

 disulphonic acid, the distribution of the colour between the residual solution and 

 silk dyed in it is governed by a law which may be expressed by the formula 



<J C in solution _ -r- 

 C in fibre 



in which C refers to the concentration of the colour solution and K is a constant 

 independent of the concentration. Later experiments have shown that this law 

 of the distribution of the colour is applicable to dyeing on silk and wool of other 

 acid colours, and also to the dyeing of direct cotton colours (salt colours) on cotton. 

 It is thus proved, first, that the processes of dyeing with the acid colours on 

 the one hand and with the direct cotton colours on the other are identical in kind ; 

 and, secondly, that these processes cannot be of a chemical nature. If a chemical 

 compound were formed, the distribution of the colour between the two media 

 would be of an entirely different character, j ust as Walker and Appleyard have 

 recently indicated. The author has only lately shown that picric acid and 

 oxyazobenzene are deposited on the fibre in a free state during dyeing with these 

 colours : this seems to be of especial importance in the case of picric acid, in view 

 of Knecht's statement, recalling the fact that picric acid forms compounds with such 

 great readiness ; chemical combination, if at all possible, might have been expected 

 in this instance. 



Binz and Schroter have lately endeavoured to show that dyeing with oxyazo- 

 benzene differs materially from that of the other acid colours. On account of the 

 fastness exhibited by dyeings with oxyazobenzene these authors assumed that this 

 colour forms a stable compound with the substance of the wool as the result of 

 condensation. 



As regards the dyeing of acid colours on animal fibres, and that of the direct 

 cotton colours on cotton, we may therefore safely say that we possess distinct proof 

 that these processes are identical and of a mechanical nature. 



The further question as to whether substantive dyeings should be considered 

 as solid solutions or as resulting from adhesion is still open for speculation. 



MONDAY, SEPTEMBER U. 

 The following Papers and Report were read : — 



1. The Slow Combustion of Methane and Ethane. 

 By William A. Bone, D.Sc, Ph.D. 



I may perhaps be allowed] to explain my reasons for reopening what I am 

 well aware is one of the most controverted questions in the whole domain of 

 Chemistry. Let me say at once that I have no new general theory of hydro- 

 carbon combustion to bring forward ; but during tbe past three or four years I 

 have, in conjunction with two of the research students at Owens College,' been 

 engaged upon an investigation on the slow combustion of methane and ethane at 

 temperatures below their ignition-points, the results of which throw some new 



' Messrs. P. V. Wheeler and W. K. Stockings. 



