396 
MR. STENHOUSE ON THE EXAMINATION OF THE 
by an acid and recrystallizing, the organic acid it contained was found to have a 
different composition from that of gyrophoric acid ; from which it also differed in its 
properties, being much more soluble in water and also more distinctly acid. 
An alcoholic solution of gyrophoric acid gives no precipitate with an alcoholic 
solution of sugar of lead, but it yields a pretty bulky precipitate with both an aqueous 
and an alcoholic solution of subacetate of lead. Though I made many trials I was 
unable to obtain these precipitates of anything approaching to an uniform composi- 
tion. Neither was I more successful in forming any other definite compounds of 
gyrophoric acid by which its atomic weight might have been more definitely ascer- 
tained. 
Lecanora tart area. 
This lichen, like the Gyrophora pustulata, has been employed from a very early 
period in the manufacture of archil. The Lecanora tartarea is found in considerable 
abundance in the hilly districts of the northern parts of both Scotland and Ireland, 
though what is usually met with in commerce is chiefly obtained from Norway and 
its neighbouring countries. The lichen on which I operated was from Norway. Its 
colouring principle was extracted by milk of lime, exactly in the way already de- 
scribed. The quantity of colouring principle it contained was, comparatively speak- 
ing, small, not exceeding that in the Gyrophora pustulata. The precipitate thrown 
down from the lime solution by muriatic acid had a brownish-red colour. It was 
washed with cold water, collected on a cloth filter and cautiously dried. It was then 
digested with a little dilute spirits, which removed a greenish coloured resinous 
substance precisely similar to that contained in the Gyrophora pustulata. The portion 
of the precipitate which did not dissolve in the weak spirits was next digested in 
strong alcohol assisted by a considerable quantity of animal charcoal. The filtered 
solution deposited the colouring principle in small silky prisms arranged in stars. 
These crystals at first had a yellowish tinge, but by being repeatedly digested with 
animal charcoal, they were rendered quite colourless. A considerable portion of the 
original gelatinous precipitate did not dissolve in the hot alcohol, and appeared, as in 
the case of the preceding lichen, to consist of a brownish coloured humus-like sub- 
stance. The purified acid from the Lecanora tartarea was dried in vacuo and burned 
with chromate of lead. 
I. 0T53 substance gave 0-342 Co^ and 0-071 water. 
II. 0-250 substance gave 0'561 Co^ and 0-115 water. 
Calculated numbers. 
Found numbers. 
per cent. 
I. 
II. 
36 C 
2700 
60-02 
61-96 
61-20 
18 H 
225 
5-09 
5-15 
5-10 
15 O 
1500 
33-89 
33-89 
33-70 
4425 
100-00 
100-00 
100-00 
