water, then filtered and the purified quinoidine precipitated by a slight excess of liquor of soda.
Prop., &c. In its crude form quinoidine somewhat resembles aloes; in its purest state it is a yellowish-brown, resin-like mass, freely soluble in alcohol and ether, but nearly insoluble in water; with the acids it forms dark-coloured, uncrystallisable salts. It is powerfully febrifuge, but less so than either quinidine or quinine, although it is identical in chemical composition with both of them.—Dose, 2 to 4 gr. for adults, 1⁄4 to 1 gr. for children, given in wine, lemonade, or acidulated honey.
QUINOM′ETRY. Syn. Cinchonometry. The art of estimating the quantity of quinine in cinchona bark, and in the commercial salts of this alkaloid.
Proc. 1. For bark.—a. (Ph. E.) A filtered decoction of 100 gr. of bark, in distilled water, 2 fl. oz., is precipitated with 1 fl. dr., or q. s. of a concentrated solution of carbonate of soda; the precipitate, after being heated in the fluid so as to become a fused mass, and having again become cold, is dried and weighed. “It should be 2 gr., or more, and entirely dissolve in a solution of oxalic acid.” To render the result strictly accurate, the product should be dissolved in 10 parts of proof spirit, containing 1⁄20th of sulphuric acid, and to this solution carefully added an alcoholic solution of iodine as long as there appears a brown precipitate, which immediately turns black by stirring with a glass rod. This precipitate, collected upon a filter, washed with strong alcohol and dried on a water bath, is Herapath’s iodosulphate of quinine, of which 100 parts represent 56·5 parts of pure quinine.
b. (Rebourdain.) 100 gr. of the bark (coarsely powdered) are exhausted with acidulated water, and the filtered solution rendered alkaline with solution of potassa; it is next shaken with about 1-3rd of its volume of chloroform, and then allowed to repose for a short time; the chloroform holding the alkaloid in solution sinks to the bottom of the vessel in a distinct stratum, from which the supernatant liquid is separated by decantation; the chloroformic solution, either at once or after being washed with a little cold water, is allowed to evaporate; the residuum, when weighed, gives the per-centage richness of the sample.
Obs. A like result may be obtained with ether instead of chloroform; in which case the solution of quinine will form the upper stratum.
c. Instead of Rebourdain’s process, Dr de Vrij prefers that of Charles,[132] so far as regards the separation of the total mixed alkaloids from the bark. To this mixture is applied the process mentioned above (a), viz. solution in acidulated proof spirit, &c.
[132] ‘Journal de Pharmacie et de Chimie,’ 4e série, t. 12, p. 81 (Août, 1870).
2. For the SALTS. The above methods, as
well as several others which have been devised for the purpose, may also be applied to the salts of quinine; but, unfortunately, they are inapplicable when great accuracy is required, owing to the non-recognition of the presence of quinidine, as such, and which, consequently, goes to swell the apparent richness of the sample in quinine. The following ingenious method, invented by Dr Ure, not merely enables us to detect the presence of cinchonine and quinidine in commercial samples of the salts of quinine, but, with some trifling modifications, it also enables us to determine the quantity of each of these alkaloids present in any sample:—“10 gr. of the salts to be examined” (the sulphate is here more especially referred to) “is put into a strong test-tube, furnished with a tight-fitting cork; to this are to be added 10 drops of dilute sulphuric acid (1 acid and 5 water), with 15 drops of water, and a gentle heat applied to accelerate solution. This having been effected, and the solution entirely cooled, 60 drops of officinal sulphuric ether, with 20 drops of liquor of ammonia, must be added, and the whole well shaken while the top is closed by the thumb. The tube is then to be closely stopped, and shaken gently from time to time, so that the bubbles of air may readily enter the layer of ether. If the salt be free from cinchonine and quinidine, or contain the latter in no greater proportion than 10%, it will be completely dissolved; while on the surface, where contact of the two layers of clear fluid takes place, the mechanical impurities only will be separated. After some time the layer of ether becomes hard and gelatinous, and no further observation is possible.”