244 
ACTION OF NITRIC ACID ON RHUBARB. 
deposit is formed, together with a crystalline pellicle over 
the surface ; but no crystals are deposited on cooling. A 
dry product is obtained by evaporating all the spirit away, 
and this is in the form of a granular powder of a brownish 
yellow color, having some resemblance to Spanish tobacco. 
It has a slightly aromatic odor, and a mucilaginous and 
slightly acid taste, quite different from that of rhubarb. 
This substance is entirely dissolved by repeatedly treat- 
ing it with hot alcohol. On evaporating the solution, a 
granular substance of a sulphur yellow color is obtained, 
the surface of which acquires an orange tint, from exposure 
to the air. 
This substance possesses all the physical and the princi- 
pal chemical characters attributed by Brandes to rhabarba- 
ric acid, and by Geiger to rhabarbarine. 
The erythrosinof indigenous and of exotic rhubarb afford 
products which are perfectly identical, excepting that that 
of indigenous rhubarb yields a larger proportion of the rha- 
barbaric acid. 
Erythrosin of indigenous rhubarb yielded : — 
Rhabarbaric acid 85.0 
Insoluble matter 15.0 
100.0 
Erythrosin of exotic rhubarb yielded : — 
Rhabarbaric acid 60.0 
Insoluble matter 40.0 
100.0 
Action of Ether. — From the action of Ether on the sub- 
stance dissolved by alcohol, it might be inferred that it is a 
perfect solvent for rhabarbaric acid. It exhausts erythrosin 
entirely of that principle when aided by the application of 
heat. 
Action of Alkalis.— -When erythrosin is brought into 
contact with the alkalis, it immediately acquires an intense 
