88 
MR. STENHOUSE ON THE EXAMINATION OF THE 
the brownish resinous matter. When pure, brom-orceid forms long white adhering 
needles. It has neither taste nor smell. The mother-liquors, from which it crystal- 
lizes, assume a pale reddish colour on standing, and contain some hydrobromic 
acid. The brom-orceid was dried in vacuo and subjected to analysis. 
I. 0'355 grin, substance gave 0-5810 AgBr=0-2439 Br=68-70 per cent, bromine. 
IL 0-407 grm. substance gave 0-665 AgBr=0-2792 Br=68-59 per cent, bromine. 
I. 0-5442 grm. substance gave 0-471 carbonic acid and 0-076 water. 
II. 0-451 
grm. gave with chromate of lead 0-391 carbonic acid and 0-065 water. 
Found numbers. 
Calculated numbers. 
I. 
II. 
66 C 
5044-710 
23-63 
23-60 
23-64 
24 H 
324-467 
1-52 
1-55 
1-60 
3Br 
14674-500 
68-75 
68-70 
68-59 
130 
1300-000 
6-10 
6-15 
6-27 
21343-677 
100-00 
100-00 
100-00 
The formula given above, Cgg IT 
>4 ^^*3 ^135 
is purely empirical. 
I regret that I have 
been unable to determine its atomic weight by the analysis of any of its compounds, 
and to establish a simple relation between it and orcin, if any such exist. Brom- 
orceid has a feeble acid reaction. It dissolves readily in alkaline solutions. These 
solutions soon grow dark-coloured, and when they are neutralized by muriatic acid, 
a yellowish resin precipitates. 
Chlor-Orceid. 
A similar compound is formed when chlorine is made to act upon orcin. In the 
course of several trials with dry orcin and with its aqueous and alkaline solutions, 
I obtained little more than traces of a crystalline chlorine compound. The crystals 
were always accompanied with a large quantity of a dark-coloured resin, which 
adhered to them so pertinaciously that I have not as yet been able to procure a suf- 
ficient quantity of the crystals to be able to subject them to analysis. Mr. Schunck 
endeavoured to prepare a similar compound, but, as he has given no analysis of it, I 
suspect that in this instance his success has been pretty similar with my own. 
Usnic Acid. 
This acid, which occurs in considerable quantity in several of the lichens, was dis- 
covered by Mr. Knop in 1843. It was also examined nearly at the same time by 
Messrs. Rochleder and Heldt. Knop found it in several species of Usnea, such as 
Vsnea jiorida, U. hirta and U. ylicata. Messrs. Rochleder and Heldt extracted it 
from the lichen Rangiferinus, Usnea harbata and RamaUnea calicaris. In addition to 
these sources, I may mention that I have found it in Evernia Prunastri, where it occurs 
along with evernic acid, and in RamaUnea Fraxinea. Knop’s process for procuring 
usnic acid is by treating the lichens in a displacement apparatus with ether. This is 
