PROXIMATE PRINCIPLES OF SOME OF THE LICHENS. 
87 
any of the different kinds of Lecanora in milk of lime, should be boiled in an open 
pan for some hours, and the liquid concentrated to about a fourth of its bulk. A 
stream of carbonic acid gas should then be sent through the liquid so long as 
carbonate of lime precipitates. The clear liquid should again be drawn off, and 
cautiously evaporated to dryness on the water-bath. The residue should then be 
boiled with three or four times its bulk of strong spirits, filtered and set aside to 
crystallize. In two or three days abundance of large dark-coloured crystals are de- 
posited in the liquor. These should be separated and dried between folds of blotting- 
paper. The dried crystals should then be dissolved in three or four times their 
weight of anhydrous ether, in which they are exceedingly soluble, and the solution 
filtered. By evaporation in vacuo the orcin crystallizes out of the etherial solution in 
large six-sided prisms, which have only a light red colour, and which by a subsequent 
crystallization, also out of ether, may be rendered still fainter. A quantity of orcin 
prepared in this way was dried under the fiir-pump for upwards of a week. It is not 
easily dried, as it is a very hygroscopic substance. When subjected to analysis, it 
gave numbers which agreed exactly with those which Mr. Schunck found for anhy- 
drous orcin. Orcin repeatedly crystallized out of anhydrous ether appears therefore to 
be anhydrous. Orcin, however, is a substance which varies so much in the quantity 
of water it contains, according to the temperature at which it has been dried, that I 
defer saying more at present than that I am engaged in examining it more minutely. 
When orcin is treated with a few drops of hypochlorite of lime, it assumes a dark 
purple red colour, which quickly changes to a deep yellow. It is quite different 
from the blood-red colour which orsellic or erythric acids yield when similarly treated, 
but it cannot be distinguished by the eye from the reaction which orsellesic and the 
other intermediate acids yield with hypochlorite of lime. 
Brom-Orceid. 
When bromine is poured into a concentrated aqueous solution of orcin an ener- 
getic action immediately ensues ; much heat is evolved, and a brownish red crystal- 
line mass falls to the bottom of the liquid. Bromine was added so long as this action 
continued, and the crystallized mass was separated from the supernatant liquor, 
which contained a great deal of hydrobromic acid, and was repeatedly washed with 
cold water. This bromine compound is but little soluble in either cold or hot water. 
In hot water it melts like a heavy oil, but crystallizes on the cooling of the liquid. 
It is very soluble in alcohol, both hot and cold, and also in ether. The brown colour 
of the crystals, when first precipitated, is owing to their being contaminated with a 
brown-coloured uncrystallizable resin. The quantity of this brownish resin is, com- 
paratively speaking, small. It also contains bromine, and has a very pungent smell, 
which affects the eyes and nose very strongly, occasioning considerable pain. The 
crystalline bromine compound, which I shall call Brom-orceid, is readily purified by 
digesting it in dilute spirits, with the aid of a little animal charcoal, which absorbs 
