For determination of quinine alkaloids, 50 c.c. are taken - conveniently in a 100 c.c. cylinder fitted with a blow-off arrangement similar to that of an ordinary wash-bottle.
The wine is made alkaline with a few drops of strong solution of ammonia, and extracted three times with about 50 c.c. of ether each time. The ethereal solutions are blown off into a tared flask, the ether is distilled off, and the residue dried and weighed. The result may be checked by dissolving the weighed alkaloid in a mixture of alcohol and ether (equal volumes), adding water and a little freshly-prepared alcoholic solution of hematoxylin, and titrating the liquid with decinormal acid. Each c.c. required = 0.0324 gram of alkaloids calculated as anhydrous quinine. Co-extracted colouring matter, however, sometimes masks the end-point of the reaction. If the weighed residue is obviously contaminated, it is well to purify it by dissolving in hydrochloric acid, extracting the acid solution with petroleum ether, then making alkaline again with ammonia and extracting with ether as before.