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DR. KANE ON THE CHEMICAL HISTORY OF ARCHIL AND LITMUS. 
If this were so, we should, however, find erythrolein existing' principally among the 
earliest products of the general breaking up of the colourless substances in the lichen, 
and erythroleic acid should co-exist in quantity with erythrolitmine among the latter 
results of gradual oxidation. This, however, is not the case. In archil, the earliest 
stage, there is but a mere trace of erythrolein and of erythrolitmine, but abundance 
(comparatively speaking) of erythroleic acid, whilst in the litmus, where the train 
of decompositions is much more advanced, scarcely a trace of erythroleic acid can 
be found, but the erythrolein makes its appearance in greater quantity, and a great 
portion of the colouring matter of the litmus is erythrolitmine, I am hence induced to 
consider these substances as formed in the following order. By the reaction already 
described, the roccelline is converted into erythroleic acid, which then breaks up into 
erythrolein and erythrolitmine, as it can be seen that 
Two atoms erythroleic acid. One erythrolein. Erythrolitmine. 
C52 h 44 0 16 == C 26 h 22 o 4 + C 26 h 22 0 12 
The erythrolein, I consider, may then absorb oxygen and form erythroleic acid, 
which will be again broken up and ultimately all converted into the final term ery- 
throlitmine. In the commencement, therefore, the erythroleic acid is tolerably per- 
manent until the roccelline is all exhausted ; and indeed its permanency is promoted 
by the fact that in making archil too rapid an oxidation might do much harm, the 
alphaorceine being a richer colour than the betaorceine. But in making litmus it is 
decomposed, and whilst the great mass rapidly forms erythrolitmine, small quantities 
of erythrolein appear to escape the action of the air. 
Finally, to sum up the results of this part of the investigation, I look upon these 
three bodies as all derived from roccelline; but notwithstanding the beautiful simplicity 
of their formulae, which would appear to indicate them to be all oxides of one com- 
pound radical, which contained C 26 H 22 , I look upon them as, when once formed, 
being quite independant of each other : thus, if erythrolitmine was erythrolein 
+ eight oxygen, we should be able, by deoxidizing means, to change erythrolitmine 
into erythrolein ; this cannot be done, and hence, as will be shown more fully when 
describing the results of decolorization of these bodies, I look upon each as having an 
internal constitution distinct from either of the others. 
III. Of Azolitmine. 
The preparation of the azolitmine has been already described ; it constitutes almost 
pure, the substance separated by means of muriatic acid, and insoluble in alcohol. 
It is sparingly soluble in water, and still more soluble in water of potash or of am- 
monia, with which it forms the peculiar blue of litmus, and may be obtained, as 
already noticed, either by evaporating the aqueous solution, or by treating the am- 
monia compound with a little muriatic acid and warm alcohol. 
As thus prepared the azolitmine is a deep brownish-red powder, totally destitute of 
crystalline texture. Its general characters of solubility, &c. are indicated by the 
