Both English and French exhibitors have also sent samples of cognac-oil and grape-oil, which are employed to flavor the common sorts of brandy. As these samples were very small, I was prevented from making an accurate analysis. However, I am certain that the grape-oil is a combination of amyl, diluted with much alcohol; since, when acted upon with concentrated sulphuric acid, and the oil freed from alcohol by washing it with water, it gave amylsulphuric acid, which was identified by the analysis of the salt of barytes.
1,2690 gram. of amylsulphate of barytes gave 0,5825 gram. of sulphate of barytes. This corresponds to 45,82 per cent. of sulphate of barytes.
Amylsulphate of barytes, crystallized with two equivalents of water, contains, according to the analysis of Cahours and Kekule, 45,95 per cent. of sulphate of barytes. It is curious to find here a body, which, on account of its noxious smell, is removed with great care from spirituous liquors, to be applied under a different form for the purpose of imparting to them a pleasant flavor. {151}
I must needs here also mention the artificial oil of bitter almonds. When Mitscherlich, in the year 1834, discovered the nitrobenzol, he would not have dreamed that this product would be manufactured for the purpose of perfumery, and, after twenty years, appear in fine labelled samples at the London Exhibition. It is true that, even at the time of the discovery of nitrobenzol, he pointed out the striking similarity of its smell to that of the oil of bitter almonds. However, at that time, the only known sources for obtaining this body were the compressed gases and the distillation of benzoic acid, consequently the enormity of its price banished any idea of employing benzol as a substitute for oil of bitter almonds. However, in the year 1845, I succeeded by means of the anilin-reaction in ascertaining the existence of benzol in common coal-tar-oil. In his essay, which contains many interesting details about the practical use of benzol, he speaks likewise of the possibility of soon obtaining sweet scented nitrobenzol in great quantity. The Exhibition has proved that this observation has not been left unnoticed by the perfumers. Among French perfumeries we have found, under the name of artificial oil of bitter almonds, and under the still more poetical name of “essence de mirbane,” several samples of essential oils, which are no more nor less than nitrobenzol. I was not able to obtain accurate details about the extent of this branch of manufacture, which seems to be of some importance. In London, this article is manufactured with success. The apparatus employed is that of Mansfield, which is very simple; it consists of a large glass worm, the upper extremity of which divides in two branches or tubes, which are provided with funnels. Through one of these funnels passes a stream of concentrated nitric acid; the other is destined as a receiver of benzol, which, for this purpose, requires not to be quite pure; at the angle from where the two tubes branch out, the two bodies meet together, and instantly the chemical combination takes place, which cools sufficiently by passing through the glass worm. The product is afterwards washed with water, and some diluted solution of carbonate of {152} soda; it is then ready for use. Notwithstanding the great physical similarity between nitrobenzol and oil of bitter almonds, there is yet a slight difference in smell which can be detected by an experienced nose. However, nitrobenzol is very useful in scenting soap, and might be employed with great advantage by confectioners and cooks, particularly on account of its safety, being entirely free from prussic acid.
There were, besides the above, several other artificial oils; they all, however, were more or less complicated, and in such small quantities, that it was impossible to ascertain their exact nature, and it was doubtful whether they had the same origin as the former.
The application of organic chemistry to perfumery is quite new; it is probable that the study of all the ethers or ethereal combinations already known, and of those which the ingenuity of the chemist is daily discovering, will enlarge the sphere of their practical applications. The caprylethers lately discovered by Bouris are remarkable for their aromatic smells (the acetate of capryloxide is possessed of the most intense and pleasant smell,) and they promise a large harvest to the manufacturers of perfumes.—Annalen der Chemie.—In An. of Pharmacy.
ON TESTS FOR THE IMPURITIES OF ACETIC ACID.
Pure acetic acid is colorless, possesses strong acid properties and taste, and no empyreumatic flavor. It should have, according to the new London Pharmacopœia, a specific gravity of 1.048, and one hundred grains should saturate eighty-seven grains of crystallized carbonate of soda; consequently the pharmacopœial acid consists of thirty-one per cent. of the anhydrous acid, and sixty-nine per cent. of water. It should leave no residuum by evaporation. Sulphuretted hydrogen, nitrate of barytes, ferrocyanuret of potash, and nitrate of silver, should produce no precipitate in it. When it contains empyreumatic {153} matter, which besides being evident to the smell, concentrated sulphuric acid causes its color to darken. Sugar, in a more or less changed condition, is frequently one of the impurities of the German diluted commercial acid, and may be recognized by the taste of the residuum left upon its evaporation.
When sulphuretted hydrogen produces in acetic acid a milky turbidity, it shows that sulphurous acid is present, the presence of which is due to the decomposition of coloring and other organic matters, contained as impurities in the acetates, from which the acetic was prepared, when treated with sulphuric acid. The turbidity is caused by the separation of sulphur from the sulphuretted hydrogen, and from the sulphurous acid by reason of the hydrogen of the former combining with the oxygen of the latter, and forming water (Wittstein.) If the sulphuretted hydrogen produces a black precipitate, either lead or copper may be present. The lead may be recognized by sulphuric acid giving a precipitate of sulphate of lead; and the copper, by the blue reaction which ensues, with an excess of ammonia. Sulphuric acid can be readily known when present by nitrate of barytes producing a white precipitate, insoluble in mineral acids. Nitrate of silver detects muriatic acid by throwing down a white precipitate, which changes, under the influence of light, to a violet color, and is insoluble in nitric acid, but soluble in ammonia. Ferrocyanuret of potassium will indicate the presence of salt of iron when by its addition, a blue precipitate results.