244 ON THE PREPARATION OF VEGETABLE ALKALOIDS. 
tive facility, though I confess that the quantity was small, lbj. of 
the root yielding me but about eight grains of the base. This I 
attribute, however, to not being able to procure the root in a good 
state of preservation. 
I have also obtained rhabarbine by this process, and as I be- 
lieve the notices of this substance at present published are rather 
vague, perhaps I shall not be trespassing too much on your time 
in giving a short account of it. 
It is of a yellow colour, and by the aid of the microscope, is seen 
to consist of long prismatic crystals ; it is fusible at a gentle heat, 
at a higher temperature, in part subliming in the form of a yellow 
powder, in part decomposing to a black mass : it is soluble in 
ether and in boiling alcohol, and insoluble in solutions of the caus- 
tic alkalies, which do not redden it. 
I do not consider the substance obtained by the process to be 
the rhabarberic acid of Brande's, for that is reddened by the alka- 
lies, and also would appear to be eliminated in the first part of the 
process, since it is precipitated by acetate of lead ; I consider it 
rather to be the " rhein" of Dulk, which he states to be the real 
principle of rhubarb, and to become rhabarberic acid by oxida- 
tion. 
Now, on the supposition that such is the case, it becomes a point 
of some interest in Pharmacy to determine whether the precipitate 
occurring in tincture of rhubarb may not be caused by the oxida- 
tion of its active principle, and how far the tincture may be dete- 
riorated by such circumstances. 
The Chairman, in reference to the allusion made in Mr. Cobb's 
paper to the elimination of the active principle of rhubarb, said, 
that a good test for distinguishing Russian from East Indian rhu- 
barb was much wanted, and suggested that probably the process 
described by Mr. Cobb might be applied for the purpose. — Phar- 
maceutical Journal and Transactions, March 1851. 
