PROXIMATE PRINCIPLES OF SOME OF THE LICHENS. 
75 
picro-erythrin, while in the case of the orsellic acids, orsellesic acid and some car- 
bonic acid are the only products. Erythrelesic acid is not quite so soluble in water 
as either of the orsellesic acids ; it crystallizes in small flat scales. When erythre- 
lesic acid is boiled for a short time in water, it is, like the two preceding acids, con- 
verted wholly into colourless orcin with evolution of carbonic acid gas. When, on 
the other hand, it is boiled with an excess of lime or baryta, it is also converted into 
orcin, which, by this process, has always a deep red colour. Erythrelesic acid forms 
a very soluble salt with baryta, which crystallizes in long four-sided prisms, which 
are flatter than those of orsellate of baryta. I intend subjecting this and its kindred 
acids to a more minute examination. The taste of erythrelesic acid is sourer and 
more bitter than the orsellesic acid, and it exhibits the same violet colour with hypo- 
chlorite of lime. 
Picro-erythrin . 
When erythric acid has been neutralized by lime or baryta and boiled, as above 
described, and the erythrelesic acid thrown down by muriatic acid, and removed, the 
mother-liquor contains a considerable amount of picro-erythrin. When the mother- 
liquor is concentrated considerably and set aside for a few days in a cold place, the 
picro-erythrin is deposited in yellowish-coloured crystals. These may be purified by 
washing them with cold water, and repeatedly crystallizing them out of boiling 
water, aided by a little animal charcoal. When pure, picro-erythrin crystallizes in 
long colourless needles arranged in stars. It has a very bitter taste, and is exceed- 
ingly soluble in hot water, but very slightly soluble in cold water. Picro-erythrin 
strikes the same blood-red colour with hypochlorite of lime as erythric acid does. 
Its solutions in ammonia, on standing for some time exposed to the air, yield a red 
compound similar to orcein. 
I. 0*5225 grm. picro-erythrin dried at 212° Fahr. and burned with chromate of 
lead, gave TO 169 carbonic acid and 0*286 water. 
II. 0*2825 grm. picro-erythrin gave 0*5527 Cog and 0*1513 water. 
Found. 
Calculated numbers. 
I. 
II. 
34 C 2598*790 
53*19 
53*07 
53*23 
23 H 287*028 
5*87 
6*08 
5*95 
20 0 2000*000 
40*94 
40*85 
40*82 
100*00 
100*00 
100*00 
The formula which I have found for picro-erythrin differs from Mr. Schunck’s by 
one atom of hydrogen, his being C 34 H 24 Ogo- 
I was unable to procure the lead salt, mentioned by Mr. Schunck, of uniform 
composition, though I made repeated attempts. I was not more successful in my 
endeavours to form a baryta salt ; the picro-erythrin crystallized out of its solution, 
retaining scarce a trace of baryta. Mr. Schunck’s description of the other properties 
^ L 2 
