318 DR. KANE ON THE CHEMICAL HISTORY OF ARCHIL AND LITMUS. 
cing a series of new bodies totally different in colour. Thus, as by exposure to oxygen, 
there are produced 
so by exposure to hydrogen, the same series should be re-produced in the inverse 
order, if it act only by removing oxygen. This, however, does not take place ; on the 
contrary, it appears that as from C 18 H 10 N 0 8 , there is formed by oxygen C 18 H 10 
N O 10 , so there is by hydrogen C 18 H 10 N O g H 2 , and perhaps from C 18 H 10 N 0 6 . 
C 18 H 10 N O s . 0 3 , and C 18 H 18 N 0 5 . H 3 , and from C 18 H 10 N O 10 hydrogen forms C 18 
H 10 N O 10 H. I conceive that in this way alone can a satisfactory explanation of ail 
the facts be given. That deoxidation is not the characteristic process, obtains also 
probability from the fact, that neither sulphurous acid, nor a solution of a sulphite, has 
any effect upon azolitmine, either free or in alkaline combination. The sulphurous acid 
reddens litmus as any other acid, but has no power whatsoever to remove its colour. 
There is no circumstance, in the history of the colouring bodies, of more interest 
than that of the bleaching powers of chlorine ; whether considered as affording the 
theory of a process, so long and so deservedly esteemed one of the most important 
applications of chemistry to the arts, or examined with regard to testing by its means 
the generality and exactness of the important views recently deduced, concerning the 
constitution of organic bodies, from the results of the action of chlorine upon them, 
by studying in a new class of substances, how far the principle on which it acts may 
be modified or confirmed. Before the study of organic chemistry had attained the 
accuracy which it now possesses, chlorine was considered to bleach by decomposing 
water, with the hydrogen of which it entered into combination. The oxygen being 
thus set free, was supposed to act in its nascent form with peculiar power upon the 
colouring matter, and thus to produce in a few minutes the same effect as should 
have resulted, though much more slowly, from the action of air and moisture. When 
the action of chlorine on organic substances became more minutely studied, it was 
found that a portion of chlorine entered into the constitution of the new substance 
formed by its action, and it was natural to suppose that such should be the case in 
bleaching also. This idea appears to have been first distinctly advanced by Robiquet 
in the article Blanchiment, in the Dictionnaire Technologique, in 1823 ; but as he did 
not rest it on any experimental evidence, it did not attract attention, and I was not 
aware that the true theory of bleaching had been suggested by that chemist until 
these researches were almost quite complete. 
In addition to the principle of the fixation of chlorine in the resulting compound, 
there is another point to be attended to in researches like the present, and which will 
be found of high interest in a theoretical point of view. In the generality of organic 
bodies, the fixation of chlorine is accompanied by loss of hydrogen, usually to an 
