DR. KANE ON THE CHEMICAL HISTORY OP ARCHIL AND LITMUS. 297 
the examination of the archil weed. Besides the erythryline, which is the origin and 
basis of the archil series, I noticed the existence in small quantity of the roccellic 
acid of Heeren, which, however, I found in so small quantity that I could not insti- 
tute any analyses of it or of its compounds. It was looked upon by Heeren as being 
distinct from the bodies which produce colour, and so far as the proper orceine (lichen- 
red) is concerned, with perfect justice, but when we consider its constitution there can 
be little doubt of its being the source of erythroleic acid. We possess an analysis 
of it by Liebig, made with a portion sent to him by Heeren, and certainly the highest 
confidence may be reposed in his result. The formula C 16 H 16 0 4 was adopted by 
Liebig, and his numbers are 
Theory. Experiment. 
Carbon . . . 6/"05 67‘94 
Hydrogen . . 1095 10'76 
Oxygen . . . 22-00 21 ‘30 
100-00 100-00 
Liebig remarks that the formula C 17 H 17 0 4 agrees still better with his results, but 
he prefers the simpler 4 (C 4 FI 4 O). A formula, however, which requires less carbon 
and more hydrogen than was obtained in the analysis of a pure substance cannot be 
adopted, and this objection applies to C 17 H 17 0 4 also, though not in so great a de- 
gree. The only support indeed which this formula receives is from an experiment 
made by Heeren, who found that the roccellate of lime contained 15’9 of lime per 
cent., the oxygen of which is one fourth that of the roccellic acid. On this isolated 
result I do not consider that much stress can be laid ; and as this roccellic acid, or as 
I propose to term it, roccelline, is the only constituent of lichen possessing hydrogen 
enough to allow of the formation of erythroleic acid, I would suggest to chemists the 
probability of its formula being rather C 26 H 24 0 6 , from which are obtained the 
numbers. 
Theory. Experiment. 
26 Carbon . = 158-6 6878 67' 94 
24 Hydrogen 24'0 10"40 1076 
6 Oxygen . 48*0 20*82 21 -30 
2306 10000 100-00 
A sesquisalt of this acid (C 26 H 24 0 6 ) + 4 Ca O should give 15 '6 of lime, and was 
perhaps that analysed by Heeren. 
The proposed formula being assumed, it is very easy to show how from it erythro- 
leic acid may be formed. 
An equivalent of roccelline = C 26 H 24 O e 
— H 2 + 0 2 
An equivalent of erythroleic acid . . . . = C 26 H 22 O g 
2 Q 
MDCCCXL. 
