ON THE ADULTERATION OF SULPHATE OF QUININE, AND THE MEANS OF DETECTION.
Mr. Zimmer, manufacturer of sulphate of quinine in Frankfort-on-the-Maine, has published the following circular and paper to his correspondents abroad:
Frankfort-on-the-Maine, Feb. 6th, 1852.
You are doubtless, aware that various and partly spurious kinds of sulphate of quinine have for some time past found their way into the market. The substance now frequently {143} mixed with quinine is quinidine. But little positive is as yet known of the medicinal properties of this alkaloid, and whatever may be the result of future experiments, its arbitrary substitution is, under any circumstances, unwarrantable, and renders all fair and honest competition almost impossible.
The importance of the subject has induced me to address a few words to you, that I may submit a simple experiment by means of which the most usual adulterations of quinine may readily be detected.
I have the honor to be, with much respect, &c.
C. ZIMMER.
The high price of genuine Bolivian Cinchona Calisaya, through the monopoly of its export, has given occasion to imports, from other districts, of Cinchonas, the quality of which widely differs from that of the Calisaya, inasmuch as they contain principally quinidine. The lower prices of these barks, regardless of their different constituents, have brought them quickly into use in many factories of quinine, whereby a large quantity of quinine, containing quinidine, has got into the market, causing an undue depreciation in the price of quinine.
The existence of this third cinchona-alkaloid is now established beyond a doubt by ultimate analysis, by the peculiarity of its salts, and by important distinctive tests; and there can be no further question, that quinidine must, equally with cinchonine, be distinguished from quinine. The external characters of sulphate of quinidine differ from those of sulphate of quinine; it has a greater specific gravity and less flocculent crystallization. In dry warm air it parts with its water of crystallization, without deliquescing or losing its crystallized aspect; lastly, it is far more soluble than sulphate of quinine in cold water and in alcohol.
One of the distinctive properties of the three alkaloids in question, viz., their behavior with ether—places in our hands a ready means of detecting the mixture of cinchonine and {144} quinidine, with quinine. Schweitzer (Lond. Med. Gazette, vol. xxi., p. 175) has already employed ether for the detection of cinchonine with complete success, and his process has, with justice, been subsequently quoted in most manuals, as it answers its purpose completely; cinchonine is known to be entirely insoluble in ether, whatever may be the quantity of ether employed. The solubility of quinidine in ether, as compared with that of quinine, is but slight; ten grains of pure sulphate of quinine dissolve in sixty drops of ether, and twenty drops of spirit of ammonia, while only one grain of sulphate of quinidine is soluble in the same quantity of the fluid; and in proportion quinine containing quinidine will always be less soluble than pure sulphate of quinine.
Guided by this fact I can recommend the following simple and very convenient process for the detection of quinidine and quinine:—
Ten grains of the salt to be examined is to put into a strong test tube, furnished with a tight-fitting cork, to this are to be added ten drops of diluted sulphuric acid, (one acid and five water) with fifteen drops of water, and a gentle heat applied to accelerate the solution. This having been affected, and the solution entirely cooled, sixty drops of officinal sulphuric ether with twenty drops of spirits 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 more readily enter the layer of ether.
If the salt examined be free from cinchonine and quinidine, or contain the latter in no greater proportion than ten per cent., 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 (in which respect the various sorts of commercial quinine differ.) After sometime longer the layer of ether becomes hard and gelatinous, after which no further observation is possible.