The Art of Perfumery, and Methods of Obtaining the Odors of Plants Part 37

ON THE APPLICATION OF ORGANIC CHEMISTRY TO PERFUMERY.

BY DR. A.W. HOFMANN,

_Professor to the Royal College of Chemistry, London_.

Cahours' excellent researches concerning the essential oil of _Gaultheria proc.u.mbens_ (a North American plant of the natural order of the Ericinae of Jussieu), which admits of so many applications in perfumery,[I] have opened a new field in this branch of industry. The introduction of this oil among compound ethers must necessarily direct the attention of perfumers[J] towards this important branch of compounds, the number of which is daily increasing by the labors of those who apply themselves to organic chemistry. The striking similarity of the smell of these ethers to that of fruit had not escaped the observation of chemistry; however, it was reserved to practical men to discover by which choice and combinations it might be possible to imitate the scent of peculiar fruits to such a nicety, that makes it probable that the scent of the fruit is owing to a natural combination identical to that produced by art; so much so, as to enable the chemist to produce from fruits the said combinations, provided he could have at his disposal a sufficient quant.i.ty to operate upon. The manufacture of artificial aromatic oils for the purpose of perfumery[K] is, of course, a recent branch of industry; nevertheless, it has already fallen into the hands of several distillers, who produce sufficient quant.i.ty to supply the trade; a fact, which has not escaped the observation of the Jury at the London Exhibition. In visiting the stalls of English and French perfumers at the Crystal Palace, we found a great variety of these chemical perfumes, the applications of which were at the same time practically ill.u.s.trated by confectionery flavored by them. However, as most of the samples of the oils sent to the Exhibition were but small, I was prevented, in many cases, from making an accurate a.n.a.lysis of them.

The largest samples were those of a compound labelled "pear-oil," which, by a.n.a.lysis, I discovered to be an alcoholic solution of pure acetate of amyloxide. Not having sufficient quant.i.ty to purify it for combustion, I dissolved it with potash, by which free fusel-oil was separated, and determined the acetic acid in the form of a silver salt.

0.3080 gram. of silver salt = 0.1997 gram. of silver.

The per centage of silver in acetate of silver is, according to

Theory, 64.68 Experiment, 64.55

The acetate of amyloxide, which, according to the usual way of preparing it, represents one part sulphuric acid, one part fusel-oil, and two parts of acetate of potash, had a striking smell of fruit, but it acquired the pleasant flavor of the jargonelle pear only after having been diluted with six times its volume of spirit of wine.

Upon further inquiry I learned that considerable quant.i.ties of this oil are manufactured by some distillers,--from fifteen to twenty pounds weekly,--and sold to confectioners, who employ it chiefly in flavoring pear-drops, which are nothing else but barley-sugar, flavored with this oil.

I found, besides the pear-oil, also an _apple-oil_, which, according to my a.n.a.lysis, is nothing but valerianate of amyloxide. Every one must recollect the insupportable smell of rotten apples which fills the laboratory whilst making valerianic acid. By operating upon this raw distillate produced with diluted potash, valerianic acid is removed, and an ether remains behind, which, diluted in five or six times its volume of spirits of wine, is possessed of the most pleasant flavor of apples.

The essential oil[L] most abundant in the Exhibition was the pine-apple oil, which, as you well know, is nothing else but the butyrate of ethyloxide. Even in this combination, like in the former, the pleasant flavor or scent is only attained by diluting the ether with alcohol. The butyric ether which is employed in Germany to flavor bad rum, is employed in England to flavor an acidulated drink called pine-apple ale.

For this purpose they generally do not employ pure butyric acid, but a product obtained by saponification of b.u.t.ter, and subsequent distillation of the soap with concentrated sulphuric acid and alcohol; which product contains, besides the butyric ether, other ethers, but nevertheless can be used for flavoring spirits. The sample I a.n.a.lyzed was purer, and appeared to have been made with pure butyric ether.

Decomposed with potash and changed into silver salt, it gave

0.4404 gram. of silver salt = 0.2437 gram. of silver.

The per centage of silver in the butyrate of silver is according to

Theory, 55.38 Experiment, 55.33

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 a.n.a.lysis. 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 was.h.i.+ng it with water, it gave amylsulphuric acid, which was identified by the a.n.a.lysis 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 a.n.a.lysis 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.

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 subst.i.tute 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; and, in the year 1849, C.B. Mansfield proved, by careful experiments, that benzol can be won without difficulty in great quant.i.ty from 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 the sweet-scented nitrobenzol in great quant.i.ty. The Exhibition has proved that his 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 gla.s.s worm, the upper extremity of which divides in two branches or tubes, which are provided with funnels. Through one of these funnels pa.s.ses 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 pa.s.sing through the gla.s.s worm. The product is afterwards washed with water, and some diluted solution of carbonate of 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_.[M] 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 so small quant.i.ties, 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 capryl-ethers lately discovered by Bouis 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._

CORRESPONDENCE FROM THE "JOURNAL OF THE SOCIETY OF ARTS."[N]

CHEMISTRY AND PERFUMERY.

SIR,

When such periodicals as "Household Words" and the "Family Herald"

contain scientific matters, treated in a manner to popularize science, all real lovers of philosophy must feel gratified; a little fiction, a little metaphor, is expected, and is accepted with the good intention with which it is given, in such popular prints; but when the "Journal of the Society of Arts" reprints quotations from such sources, without modifying or correcting their expressions, it conveys to its readers a tissue of fiction rather too flimsy to bear a truthful a.n.a.lysis.[O]

In the article on Chemistry and Perfumery, in No. 47, you quote that "some of the most delicate perfumes are now made by chemical artifice, and not, as of old, by distilling them from flowers." Now, sir, this statement conveys to the public a very erroneous idea; because the substances afterwards spoken of are named essences of fruit, and not essences of flowers, and the essences of fruits named in your article never are, and never can be, used in perfumery. This a.s.sertion is based on practical experience. The artificial essences of fruits are ethers: when poured upon a handkerchief, and held up to the nose, they act, as is well known, like chloroform. Dare a perfumer sell a bottle of such a preparation to an "unprotected female?"

Again, you quote that "the drainings of cow-houses are the main source to which the manufacturer applies for the production of his most delicate and admired perfumes."

Shade of Munchausen! must I refute this by calling your attention to the fact that in the south of France more than 80,000 persons are employed, directly and indirectly, in the cultivation of flowers, and in the extraction of their odors for the use of perfumers? that Italy cultivates flowers for the same purpose to an extent employing land as extensive as the whole of some English counties? that tracts of flower-farms exist in the Balkan, in Turkey, more extensive than the whole of Yorks.h.i.+re? Our own flower-farms at Mitcham, in Surrey, need not be mentioned in comparison, although important. These, sir, are the main sources of perfumes. There are other sources at Thibet, Tonquin, and in the West Indies; but enough has been said, I hope, to refute the cow-house story. This story is founded on the fact that Benzoic acid _can be_ obtained from the draining of stables, and that Benzoic acid has rather a pleasant odor. Some of the largest wholesale perfumers use five or six pounds of gum benzoin per annum, but none use the benzoic acid. The lozenge-makers consume the most of this article when prepared for commercial purposes; as also the fruit essences. Those of your readers interested in what _really is used_ in perfumery, are referred to the last six numbers of the "Annals of Pharmacy and Practical Chemistry," article "Perfumery."

Your obedient servant, SEPTIMUS PIESSE.

CHEMISTRY AND PERFUMERY.[P]

SIR,

The discussion about chemistry and perfumery, in reality amounts to this: Mr. Septimus Piesse confines the term "perfumery" to such things as Eau de Cologne, &c.; perfumed soaps, groceries, &c., he does not appear to cla.s.s as "perfumery." Now the artificial scents are as yet chiefly used for the latter substances, which in common language, and, I should say, in a perfumer's nomenclature also, would be included in perfumery. The authority for cows' urine being used for perfumery is to be found in a little French work called, I believe, "La Chimie de l'Odorat" in which a full description is given of the collection of fresh urine and its application to this purpose. I need scarcely say, that it is the benzoic acid of the urine which is the odoriferous principle.

Your obedient servant, A PERFUMER.

[When benzoic acid is prepared by any of the wet processes, it is _free from the fragrant volatile oil_ which accompanies it when prepared by sublimation from the resin, and to which oil the acid of commerce owes its peculiar odor. This fact completely nullifies the above a.s.sertion.--SEPTIMUS PIESSE.]

CHEMISTRY AND PERFUMERY.[Q]

Sir,

If the author of the Letter on Chemistry and Perfumery, published in No.

50 of your Journal, and intended as a reply to mine--though none was needed--which appeared in No. 49, really be a perfumer, as his signature implies, he would know that I could not, though ever so inclined, "confine the term perfumery" to various odoriferous substances, and exclude scented soaps; because he would be aware that one-third of the returns of every manufacturing perfumer is derived from perfumed soap. I do however emphatically exclude from the term perfumery, "groceries, &c.," the _et caetera_ meaning, I presume, "confectionery," because perfumery has to do with one of the senses, SMELLING, while groceries, &c., are distinguishable by another, TASTE; and had not our physical faculties clearly made the distinction, commerce and manufactures would have defined them: I therefore repeat, that the artificial essences of fruits are not used in perfumery, as stated in No. 47, from the quoted authorities. If any man can deny this a.s.sertion, let him now do so, "or forever after hold his peace," at least upon this subject. The "Journal of the Society of Arts" is not a medium of mere controversy. If a statement be made in error, let truth correct it, which, if gain-sayed, it should be done, not under the veil of an anonymous correspondent, but with a name to support the a.s.sertion.

Science has to deal with tangible facts and figures, to the political alone belongs the anonymous ink-spiller.

I am, sir, yours faithfully, SEPTIMUS PIESSE.

42 Chapel Street, Edgware Road.

[If the word _flavor_ had been used by the various authors who have written upon this subject, in place of the word _perfume_, the dissemination of an erroneous idea would have been prevented: the word perfume, applied to pear-oil, pine-apple oil, &c., implies, and the general tenor of the remarks of the writers leads the reader to infer, that these substances are used by perfumers, who not only do not, but cannot use them in their trade.

But for _flavoring_ nectar, lozenges, sweetmeats, &c., these ethers, or oils as the writers term them, are extensively used, and quite in accordance with a.s.sertions of Hoffman, Playfair, Fehling, and Bastick.

However, the glorious achievements of modern chemistry have not lost anything by this misapplication of a trade term.--SEPTIMUS PIESSE.]