PROXIMATE PRINCIPLES OF SOME OF THE LICHENS. 
399 
which it bears to orcine both in the mode of its formation and in most of its pro- 
perties. Beta-orcine may be obtained by two processes ; either by destructively di- 
stilling usnic acid, or by acting on that body by alkalies. It crystallizes very beauti- 
fully in four-sided prisms surmounted at either end by well-defined four-sided pyra- 
mids. It is very soluble in water, alcohol and ether. Its solutions are perfectly 
neutral. Its crystals are hard and brittle, have a brilliant lustre, and are usually 
from an inch to three quarters of an inch long. 
Beta-orcine has a faintly sweetish taste. In the course of a few minutes it assumes 
with ammonia a beautiful blood-red colour, which on standing becomes deeper. 
Beta-orcine is therefore much more rapidly acted on by ammonia than ordinary 
orcine. The smallest portion of beta-orcine instantly strikes a bright blood-red 
colour with a solution of hypochlorite of lime ; just as alpha and beta orsellic acids, 
erythric, lecanoric and gyrophoric acids do with the same reagent. Ordinary orcine, 
on the other hand, yields a violet purple colour with hypochlorite of lime. The 
formula which I now propose for beta-orcine is C^g Hjo O4, that of orcine being 
C44H8O4. I have inserted this short notice of beta-orcine merely to complete the 
series of this class of bodies. 
Quint onitr at ed-erythromannite. 
In the former paper on the lichens, already so often referred to, I have described 
under the name of pseudo-orcine, a remarkably beautiful crystalline body, which is 
obtained by boiling either picro-erythrin or erythric acid itself, with an excess of lime 
or baryta. I have subsequently been induced to change the name of this compound 
to that of erythromannite, as indicating at once its origin and its most characteristic 
properties. It was mentioned in the previous paper that I then regarded erythro- 
mannite as very analogous to rnannite in its properties, and from an experiment I 
have recently made this conjecture has received very ample confirmation. About 
two years ago, Messrs. Flores Domonte and Menard obtained a curious detonating 
compound by dissolving rnannite in fuming nitric acid kept carefully cooled, and 
then adding an equal bulk of sulphuric acid to the solution. The compound, which 
is crystalline, is deposited on the cooling of the liquid. It is first washed wdth cold 
water, in which it is insoluble, to free it from adhering acid, and then dissolved in 
boiling spirits of wine, out of which it crystallizes in long silky needles. Mannite- 
quintinitrique, as these French chemists have called it, possesses the remarkable 
property of detonating so violently when struck with a hammer, that M. Sobrero 
has proposed employing it for the manufacture of percussion caps instead of fulmi- 
nate of mercury. 
As might naturally have been expected, from the great similarity in composition 
and properties which rnannite and erythromannite have to each other, erythromannite, 
when treated with fuming nitric acid, also yields a nitrated compound perfectly ana- 
logous to quintonitrated-mannite. In order to prepare this compound certain pre- 
3 F 2 
