The other method, which is preferable, consists in adding to the solution a little sulphate of magnesia, and then a quantity of alcohol, but not enough of the latter to produce any immediate precipitation. If a precipitate is formed immediately, {201} water is added, for, singularly enough, it was found that the liquid filtered from this first precipitate still contained lime. In the course of time the sulphate of lime separates in the form of small crystals.
The filtered liquid is now evaporated in porcelain dishes, and the residue transferred to porcelain crucibles, or still better, to platinum dishes, and the nitric acid expelled by a gentle heat. By a slight modification I have succeeded in shortening this operation very much, that is by adding, from time to time, powdered carbonate of ammonia to the mass, and stirring with a glass rod, or a platinum spatula. When no more red gases are evolved the heat is raised to redness for a few minutes. The mass thus obtained requires washing with pure water to separate alkaline salts and some sulphate of magnesia which it still contains.
Magnesia thus prepared was found, by a most rigid qualitative analysis, to be perfectly pure. I am aware, however, that the process is a troublesome one, and it is very much to be desired that some one would present us with a simple and direct process of obtaining pure magnesia from the sulphate.
ON TINCTURE OF IPECACUANHA. BY G. F. LEROY, OF BRUSSELS.
Officinal preparations during reposition or preservation, when placed in situations proper to preserve them from all changes, yet undergo such important modifications, that the pharmaceutist is frequently obliged to reject them as worthless. We are accustomed to consider alcoholic tinctures, by reason of the vehicle used in their preparation, as amongst the most stable of officinal preparations; and therefore very few {202} pharmacologists have observed the changes they undergo. Amongst those whose attention has been drawn to the subject, I may particularly cite: 1st, Baumé, who has remarked that tincture of saffron deposits a substance analagous to amber.—(Elements of Pharmacy, 2d ed. 1789.)
2nd. Guibourt, who presented to the Academy of Medicine at Paris, some observations on the changes in its composition which tincture of iodine undergoes according to the time when it was prepared, (year 1846.)
3rd. Bastick, with the desire of ascertaining the nature of the changes to which alcoholic preparations are subject, placed various tinctures, during several months, in situations similar to those of a pharmacy, that is to say, exposed to a temperature varying from 60° to 80° Fahrenheit, in bottles half filled, and to which air was, from time to time, admitted.
On examining them, some time afterwards, he found that most of them had undergone active fermentation in a greater or less degree, and that the alcohol had gradually become converted into acetic acid. The tinctures had generally lost their color and taste, and contained a precipitate which was partially re-soluble in a proportion of alcohol corresponding to that which had been decomposed.—(Pharmaceutical Journal and Transactions, 1848.)
The tinctures prepared with weak alcohol are the most subject to this species of change.