298 DR. KANE ON THE CHEMICAL HISTORY OF ARCHIL AND LITMUS. 
The characteristic constituents of archil, viz. 
1. Azoerythrine. 
2. Alphaorceine. 
3. Betaorceine. 
4. Erythroleic acid. 
having been now described., and the decompositions by which they originated having 
been reduced to laws, I shall proceed to the next portion of my subject, the constitu- 
tion of ordinary litmus. 
Section III. Of Litmus. 
In order to obtain in an isolated form the constituents of litmus, the following me- 
thod was had recourse to. 
The cubical masses of commercial litmus having been reduced to a fine powder, 
are first treated with boiling water as long as the solution comes away much coloured 
The mass of insoluble matter which remains, and which is of a paler blue than the 
original substance, is to be then diffused through water so as to form a thin cream, 
and muriatic acid added until all effervescence has ceased, and the thick opaque 
brick-red liquor reacts very acid. The whole is to be thrown upon a filter, and the 
red substance which remains is to be washed with water until all excess of muriatic 
acid has been removed, and is then to be carefully desiccated. 
When completely dry, this mass is to be boiled in successive portions of alcohol, 
until every thing soluble in that fluid shall have been taken up. The deep red alco- 
holic liquors are to be then distilled in a water-bath to dryness, and the resulting 
solid material digested in warm sulphuric ether until it no longer becomes coloured. 
The ethereal solutions thus obtained, yield on distillation in a water-bath a fine crim- 
son oily material, which is nearly fluid. To obtain this free from some of the other 
substances which the larger quantity of ether might have taken up, it may be redis- 
solved in a small quantity of ether, and the solution after standing for some hours, 
decanted from any trace of insoluble matter, and evaporated to expel ail the ether, 
for which purpose exposure for some time to a temperature above 212° is requisite. 
To the substance thus obtained I give the name of JGrythrolein. 
The substance from which the erythrolein has thus been removed, and which is 
distinguished by its solubility in alcohol, must be dried in a current of air at a tem- 
perature of 212° to expel all residual traces of ether, and may then be considered 
pure. To it I give the name of Erythrolitmine. 
The brownish red mass which resisted the action of the alcohol, yields its colouring 
material but very sparingly to water also. To obtain it in an isolated form, one or other 
of two plans may be followed. 1st, The reddish brown mass may be boiled in large 
quantities of pure water, which becomes coloured pretty deeply, and by evaporating 
these reunited liquors, a deep blood-red mass is obtained, consisting of pure colour- 
