{26}
ON THE ESTIMATION OF THE STRENGTH OF MEDICINAL HYDROCYANIC ACID, OF BITTER ALMOND WATER, AND OF CHERRY LAUREL WATER. BY J. LIEBIG.
Liquids which contain prussic acid, and are mixed with caustic potash ley until they have a strong alkaline reaction, yield, on the gradual addition of a diluted solution of nitrate of silver, a precipitate, which, on being shaken, disappears to a certain extent. Alkaline liquids containing prussic acid, may also be mixed with a few drops of a solution of common salt without the production of any permanent precipitate, until at last, on an increased addition, chloride of silver falls down.
This phenomenon depends on the fact that oxide of silver and chloride of silver are soluble in the generated cyanide of potassium, until there is found a double salt, composed of equal equivalents of cyanide of potassium and cyanide of silver, which is not decomposed by an excess of alkali. Liebig’s method of estimating the prussic acid consists in determining the quantity of silver which must be added to an alkaline liquid, containing prussic acid, until a precipitate appears. Each equivalent of silver corresponds to two equivalents of prussic acid. Having caused several experiments to be made, which prove the efficacy of this method; and having carefully observed that the presence of formic acid and muriatic acid in the prussic acid, does not interfere with the correctness of this method, the author gives the following directions for examining different liquids containing prussic acid:—The aqua amygdalarum amarum being turbid, must be clarified by the addition of a known quantity of water: 63 grs. of fused nitrate of silver are dissolved in 5937 grs. of water; 300 grs. of this liquid corresponds to 1 gr. of anhydrous prussic acid. Before applying the test, the vessel with the solution of silver is to be weighed, and of the latter so much is added to a weighed quantity (e.g. 60 grs.) of prussic acid, mixed with a small portion of potash ley and a few drops of a solution of common salt, shaking it in a common white medicine glass until a perceptible turbidness takes place, and does not disappear on shaking. The solution of silver is now again to be weighed; and supposing 360 grs. are found to have been employed for the test, the 60 grs. of the tested prussic acid contain 1,20 grs. anhydrous prussic acid, or 100 grs. contain two grains. {27}
Aqua laurocerasi, which the author examined, contained in one litre, one decigram, and the same quantity of aqua amygdal. amar. 7·5 decigrammes of anhydrous prussic acid.—(In Pharmaceutical Journal, from Ann. de Chem. U. Pharm. Bd. lxxvii.)
THE PHARMACOPŒIA OF THE UNITED STATES OF AMERICA.
The appearance of a new edition of the Pharmacopœia is to the apothecary always a matter of high interest; to it he looks for the recognized improvements in the various processes which he has constantly to perform; by it essentially he is to be guided in all the officinal preparations which he makes; and from it he learns what new articles, by their intrinsic merits and through the vogue they have obtained, are deemed of sufficient importance to be recognized officinally as additions to the materia medica. The general arrangement of the new Pharmacopœia is the same as that of 1840. Owing to the wise principles which governed the earlier framers of the Pharmacopœia—though, from the progress of botanical science, the scientific names of the plants to which many of the articles of the vegetable materia medics are referred, have been changed, and with improvements in chemistry, the nomenclature of several salts has been altered—this has led to little alteration in the designations employed in the Pharmacopœia. Assafœtida is now referred to Narthex Assafetida, instead of Ferula A.; Diosma is, after the Edinburgh Pharmacopœia, termed Barosma; Camphor to Camphora officinarum; Cardamom to Elettaria Cardamomum; Cinchona flava to C. calisaya; Cinchona pallida to C. condaminea and C. micrantha, while the source of Cinchona rubra is not yet indicated. Colocynth is now termed the fruit of Citrullus colocynthis; kino is said to be the inspissated juice of Pterocarpus marsupium, and of other plants; quassia is referred to Simaruba excelsa, and uva ursi to Artostaphylos uva-ursi.
Of the names of the articles of the materia medica, as was before stated, very few are changed. Myroxylon, of the old Pharmacopœia, is now Balsamum Peruvianum, Tolutanum, Balsamum Tolutanum; Diosma, {28} after the Edinburgh Pharmacopœia, is now Buchu; Zinci carbonas is changed to the old name, calamina; iodinum, following the British Pharmacopœias, is iodinium, and brominum, brominium. Port wine has been introduced, and consequently, instead of the Vinum of 1840, we have now Vinum Album, Sherry, and Vinum Rubrum, Port Wine.
The secondary list of the materia medica, a peculiarity of our national pharmacopœia, is still retained, to what good purpose it is hard to understand. The framers of the book state that “it has the advantage of permitting a discrimination between medicines of acknowledged value and others of less estimation, which, however, may still have claims to notice.” The advantage is not a very evident one. The distinction that is attempted is very difficult to make satisfactorily; it will vary with individuals, and, we fancy, too, with the place at which it is made. Certainly few in New York would put Angostura bark with Horsemint (Monarda), and Queen’s root (Stillingia) in the primary list; while Apocynum cannabinum, one of the most active of our diuretics, and Malefern, in tape-worm, one of the most certain anthelmintics, are exiled to the secondary. If popular, instead of professional reputation, is to be the criterion, are not Arnica, and Matricaria, and Benne leaves, and horehound, quite as well entitled to a place in the primary list as many of the articles that now figure there? And are there not twenty simples in use among the old women of the country that deserve a place in the national Pharmacopœia as well as may weed, and frost wort, and fever root? Though, too, new articles should not readily be admitted until time has fixed their value, we should like to have seen some notice of Matico and of the salts of Valerianic acid. We are sorry, too, to see the old definition of rhubarb still adhered to; “the root of Rheum palmatum and of other species of Rheum;” that of the Edinburgh Pharmacopœia, “the root of an unknown species of Rheum,” thus rendering the Russian or Chinese rhubarb alone officinal, is very much preferable.