34 ON QUINOIDINE. 
it is thrown into the acid. After the lapse of twenty-four 
or thirty-six hours, the mixture is copiously diluted with 
water, and the deep greyish-brown substance which sepa- 
rates during this process, is filtered off. The latter, well 
washed, forms, if dry, a loose, amorphous, almost black, 
not bitter mass (four ounces of the best crude quinoidine, 
gave two drachms of it.) To the filtered liquid (which is 
clear, dark blue or brown, of an acid, and afterwards bitter 
taste,) whilst boiling, crystallized carbonate of soda is 
added, until a whitish precipitate forms — a dark brown 
resinous mass having already separated on the liquid having 
been saturated with the carbonate of soda. The white 
precipitate being formed, as much crystallized sulphate of 
soda is added, as of carbonate of soda used. The mixture 
is frequently stirred, boiled in the water-bath for about a 
quarter of an hour, and then allowed to cool. After some 
time, the thin film of pale yellow, transparent, resinous 
compound covering the surface having been removed, a 
somewhat hard, resinous, bitter, almost black substance, 
often covered with some cinchonia, is found at the bottom 
of the vessel. The compound which covered the liquid is 
quinoidine, in a purer state ; it is to be placed in the vessel 
intended to receive the filtered solution, whilst the filtrate 
is mixed with the required quantity of carbonate of soda 
for the effectual separation of the alkaloid. The almost 
white precipitate which had formed, dries up, in a few 
minutes, to a resinous mass, and is now repeatedly washed 
whh hot distilled water. A considerable proportion of quinoi- 
dine remains, however, still in the precipitated resinous sub- 
stance ; the same is, therefore, pulverized, and for some 
time digested with diluted acetic acid of about five per 
cent., till nothing more dissolves. The filtrate is mixed 
with sulphate of soda, by which a considerable quantity of 
an almost black resin separates, which adheres to the sides 
of the vessel. The filtered fluid which is of a wine-yellow 
