OX QUINOIDINE. 
43 
soluble residue dried by the heat of a water-bath, and 
weighed. The insoluble part should not amount to more 
than thirty per cent, of the dried specimen. After the resi- 
due of the ethereal solution has stood for several days, it 
should be examined under a microscope, when it will be 
found to contain two kinds of crystals, one small and aci- 
cu l ar — the other larger, in rhombic prisms. The former of 
these is quinine, the latter cinchonine, the proportions of 
which vary in different specimens. 
I have met with no specimens, at present offered for sale 
in the London market, in which the presence of foreign 
matter was indicated by the tests (a) and (b). On treating 
different specimens with ether, as described (c), considerable 
difference is indicated. Some specimens contain as much 
as thirty-five per cent, of insoluble matter, while from one 
specimen that I have examined, there was only twenty-five 
per cent, of residue. 
There is a difference in the appearance of the insoluble 
residue obtained from different specimens; in some cases it 
is much darker coloured than in others. The specimen 
yielding twenty-five per cent, of residue, is the best that I 
have met with ; when reduced to powder, it is of a light 
brown colour; it forms a solution in spirit, or in water with 
the addition of an acid, which is not so nauseous in taste, 
as similar solutions formed from some other specimens, not 
excepting the patented preparation. Moreover, the portion 
insoluble in ether, is of a much lighter colour than that ob- 
tained from the other specimens. This specimen appears 
to have been less exposed than the others to heat and other 
decomposing agencies. 
I understand that some amorphous quinine, prepared 
according to Liebig's process, by solution in ether, has 
been made ; but this will not, probably, be offered for sale, 
until the specification of the patent has been filed, when it 
will be known what the patentee's process is, and how far 
it will affect the manufacture and sale of Liebig's prepara- 
tion by other parties. 
