PROXIMATE PRINCIPLES OF SOME OF THE LICHENS. 
69 
Roccella tinctoria from the Cape of Good Hope. 
This lichen, the history and botanical characters of which were partially described 
in a previous part of this paper, was pronounced by Dr. Scouler to be also a large 
variety of the Roccella tinctoria. It contains two crystalline principles, one very 
similar to orsellic acid, and another with much less determinately acid characters, to 
which I have given the provisional name of roccellinin. These two principles may 
be both extracted by treating the lichen with milk of lime, and precipitating with 
muriatic acid in the way already described. The gelatinous mass which precipitates 
consists of a mixture of both principles ; but they may be easily separated, as the 
roccellinin is quite insoluble both in cold and in hot water, while the acid analogous 
to orsellic acid, and which I purpose to call (beta) orsellic acid, is pretty readily 
soluble in boiling water. By repeatedly treating therefore the mixture of the two 
substances with boiling water and filtering, the (beta) orsellic acid is dissolved and 
deposited on the cooling of the liquid in small silky crystals. These crystals may 
be obtained quite white and of a much larger size by repeatedly crystallizing them 
out of weak spirits, care being taken not to boil the solutions. The (beta) orsellic 
acid m.ay also be prepared by boiling the lichen repeatedly with water, in the way 
already described for (alpha) orsellic acid. The orsellic acid prepared by this pro- 
cess crystallizes in small silky needles, which are quite free from roccellinin, but 
which still retain traces of a fatty acid and a little resin, from which I could only 
purify them by dissolving them in lime or baryta water, precipitating by muriatic 
acid, and treating them in the way already described. 
{Beta) Orsellic Acid. 
The following are the characters of (beta) orsellic acid when purified by repeated 
crystallizations out of weak spirits. Its aqueous and alcoholic solutions redden 
litmus paper. It is soluble in hot and cold alcohol, and in ether. A solution of 
hypochlorite of lime yields the same fugitive blood-red colour with it as with (alpha) 
orsellic acid, with erythric acid, and with the colouring principle in Lecanora tartarea. 
The action of ammonia on all these bodies appears perfectly similar. (Beta) orsellic 
acid yields but a trifling precipitate with acetate, but a bulky white precipitate with 
subacetate of lead. In short, it is intermediate in its properties between (alpha) 
orsellic acid and erythric acid, but approaches the former more closely. 
I. 0 2535 grm. acid dried at 212° Fahr., gave with chromate of lead 0'558 carbonic 
acid and 0T155 water. 
II. 0*2555 grm. substance gave 0*564 carbonic acid and 0*121 water. 
Calculated numbers. 
Found numbers. 
• I. II. 
34 C 2598*790 60*10 60 07 60*20 
18 H 224*631 5*19 5*06 5*26 
15 0 1500*000 34-71 34*87 34*54 
4323*421 100*00 100*00 100*00 
The rational formula of the hydrated (beta) orsellic acid is € 34 , 1 ^ 17 , O 44 +HO. 
