NOTE ON THE PREPARATION OF BESTUCHEFF’S TINCTURE. BY FR. MAŸER.
Pure sesqui-chloride and poto-chloride of iron are unknown to the Pharmacopœia of the United States, a fact which seems strange to a German pharmaceutist, since they are met with in every German dispensatory, and require great care for their proper preparation.
The American Pharmacopœia indeed recognizes a tincture of chloride of iron, prepared by dissolving the sub-carbonate (sesqui oxide) of iron in hydrochloric acid, and adding alcohol. This tincture would be rejected throughout Germany, since they endeavor there to obtain the preparations of perchloride of iron free from any traces of sesqui-chloride, while those of the sesqui-chloride should contain no admixture of the proto salt. This shows the practical character of the American {234} Pharmacopœia, which does not demand of the apothecary a purity of preparation which it is next to impossible to meet.
While making this acknowledgment, a good formula for the preparation of sesqui-chloride of iron still remains desirable.—This drug too, is sometimes used in American practice, as may be seen from the “Notes on Pharmacy,” by Mr. Benjamin Canavan, in the May number of the New York Journal of Pharmacy. Mr. Canavan has given one of the oldest formulæ from the Austrian Pharmacopœia of 1820, as found in the Pharmacopie Universelle by Jourdan. This formula directs us to dissolve the iron in a kind of aqua regia, and then to evaporate the superfluous acid by means of a sand bath. The sesqui-chloride thus obtained is employed in the preparation of “Bestucheff’s tincture,” by dissolving one ounce of it in an ounce of water, adding twelve ounces of ether and agitating, then decanting the ethereal solution, and finally mixing it with four times its bulk of alcohol.
Having had frequent occasion to prepare this tincture as well in Germany as in this city, it may not be unsuitable if I give here the formula for its preparation, which seems to me the most convenient, as well as my reasons for thinking so.
The sesqui-chloride of iron may be obtained in a pure and neutral state, by passing a current of chlorine gas through a solution of proto-chloride of iron, until a solution of the red ferrocyanide of potassium of Gmelin no longer produces a blue precipitate, and then evaporating the solution by means of a water bath. In this manner the salt can readily be obtained in a crystalline form. One ounce of the crystals thus obtained is to be dissolved in twelve ounces of ether, if we retain the alleged proportions, mixed with four times its bulk of alcohol, and finally bleached by exposing it to the direct light of the sun.
The Prussian Pharmacopœia of 1846 gives the following proportions:—One drachm of the sesqui-chloride of iron, or two drachms of the aqueous solution, one fluid ounce of ether, and three fluid ounces of alcohol. {235}
Here we have to notice,—1st, That it is preferable to take ether and alcohol by weight rather than by measure, since their volume is very much influenced by the temperature, which may range from 32° to 60° or 80.°
2nd, That the sesqui-chloride, prepared with nitro-nuriatic acid, is not so easy to obtain in crystals, in consequence of the adhering nitro-nuriatic acid, which is always retained in small quantities. On the other hand, by drying the salt you will, in almost every case, spoil a quantity of it by driving off too much of the acid.