D. Adulteration with Paraffin, Spermaceti, or Wax.
This mode of adulteration is practised mainly with viscid oils which congeal at rather high temperatures, such as oils of anise, rose, etc., the essential oils being usually mixed at the same time with oil of turpentine or paraffin. The fraud is easily detected by fractional distillation.
Oil of bitter almonds is often adulterated with oil of mirbane; this can be demonstrated by shaking 1 volume of the oil with 17 volumes of alcohol of 45%, and setting the mixture aside to settle. The nitrobenzol (oil of mirbane) will then collect at the bottom. Oil of Rose may be tested as follows: Mix the oil with an equal quantity of concentrated sulphuric acid. Neither the color nor the odor of the oil should be changed, but if oil of geranium was present a disagreeable odor and a darker color is produced.
It has been proposed, too, to test the oils by heating with iodine or nitric acid and determining the purity by the reaction; but the results with the different oils are so similar that the test is almost worthless. We have had the same experience with the test by nitro-prusside of copper which on being heated with essential oils gives colored precipitates differing with various oils, but still so similar that they cannot be relied upon. We have found in all cases that a comparison of an oil with a sample of known purity is the best, or else the tests given in the preceding pages.
[CHAPTER X.]
THE ESSENCES OR EXTRACTS EMPLOYED IN PERFUMERY.
The term essence or extract in perfumery means a solution of an aromatic substance in strong alcohol. These solutions are generally made as concentrated as possible and in this form find application in the manufacture of handkerchief perfumes and of certain odors bearing a special name. The so-called extrait d’œillet, extract of pink, or the favorite perfumes known as new-mown hay have nothing in common with either pink or hay except the name; like many other odors, both are merely mixtures of different essences or extracts.
Besides the manufacture of true perfumes, essences or extracts are also used for scenting fine soaps, sachets, mouth washes, etc. For the latter, too, use is often made of the so-called aromatic waters (eaux aromatisées) which are obtained as a by-product in the distillation of fragrant plants, and have a very fine odor owing to the small amount of the aromatic substance they hold in solution. To this class belong orange-flower water (Aqua Naphæ triplex, eau de fleurs d’oranges), peppermint water (Aqua Menthæ, eau de menthe), and many others.
Essences or extracts can be made in two ways: in the case of aromatic substances which are obtainable in the pure state—that is, essential oils—by dissolving them in strong alcohol in definite proportions; in the case of aromatics combined with a fatty substance by one of the processes described above, by treating the pomade (lard, or other perfectly bland, sweet, and in itself odorless fat combined with the aromatic) or huile antique (fixed oil holding the aromatic substance in solution) with the strongest alcohol.
According to the action of the alcohol upon the pomade or huile antique at ordinary or higher temperature, the process is called cold or warm infusion. Cold infusion furnishes the odor in a much more delicate and superior form than the warm. The cold infusion requires for complete solution of the aromatic four to six weeks; the warm, ten to fourteen days. Although the former consumes a much longer time, it is to be preferred, as the heat injures the odor. Pomades or huiles antiques are never completely exhausted by a single treatment with alcohol. Even when heat is employed they always retain a portion of the aromatic with great tenacity; a second and third infusion still abstracts odor from them, and finally nothing remains but pure fat with a pleasant odor which is stained and sold commercially as pomade under the name of the respective odor—violet, orange flower, reseda, etc.—or else is used over again in the factory for the extraction of flowers.
Experience has shown us that it is best to infuse the pomades or huiles antiques twice in the cold and to use the two fluids united for the finest perfumes; the residue by warm infusion furnishes an essence of second quality, and superior pomades or fragrant oils. The infusion is generally effected in strong glass bottles of a capacity of three to five gallons; about five to six quarts of cologne spirit being poured over six to eight pounds or pints of fat or huile antique.
In treating huiles antiques all parts of the oil should be brought into contact with the alcohol as much as possible, hence the bottles must be frequently shaken; a better plan is to bring the tightly closed bottles into an apparatus in which they are constantly agitated by rotation. Such an apparatus is easily made by placing the bottles in an inclined position between two rods fastened to a common axis which is kept revolving. The adjoining illustration (Fig. 32) shows such a contrivance which is required also in the manufacture of perfumes. The rotation may be effected by clockwork, water power, or any other motor.
Fig. 32.
Pomades being solid must be divided into small pieces which may be done with a knife, but the following procedure is more suitable and less laborious. The pomade is placed in a tin cylinder four inches wide and about a foot high, which is open at one end, the other being closed with a tin plate having several fine openings. The cylinder filled with pomade is set upon the bottle containing the alcohol for extraction, and the pomade is pressed through the openings in the shape of thin threads by means of a piston.
In this way, of course, the pomade acquires a very large surface and rapidly yields the aromatic substance to the alcohol. The odor of the pomade differs according to the length of time which it has been subjected to the flowers, and on being treated with alcohol furnishes extracts of corresponding strength. This should be borne in mind in the manufacture of perfumes which are intended to be uniform in quality.
After two cold and one warm infusion of the pomade, it may be made to yield some more aromatic material by heating it carefully to its exact melting-point, when extract again appears on the surface and can be poured off by gentle inclination of the vessel.
In the following pages we give the proportions by weight and measure employed by the most important French, English, and German manufacturers for their pomade extracts or solutions of the essential oils in alcohol. As to the latter we again repeat that it must be over 88 to 90% strength according to Tralles or even stronger, and that it must be absolutely free from any trace of amyl alcohol (potato fusel oil), the least amount of which impairs the delicacy of the odor. In this country (the United States) there is no difficulty whatever in obtaining alcohol of proper strength. The market offers scarcely any other but that of 94%. Of course deodorized alcohol, or so-called Cologne spirit should be used. Grain and wine spirits are the kinds which when rectified are to be preferred to all others. All the citron oils (i.e., oils of lemon, bergamot, and those with similar odor), rose oils (oils of rose, geranium, and rhodium), and many other sweet scents are most fragrant when dissolved in pure spirit of wine, while the odors from the animal kingdom and those of violet (violet and orris root) smell sweetest when dissolved in grain spirit.
The essences prepared from pomades or huiles antiques usually contain in solution some fat which is best removed by cooling. To this end the vessels containing the essences are placed in a vat and surrounded with pellets of ice and crystals of chloride of calcium. By this mixture the temperature can be reduced below-20° C. (-4° F.), and after some time the fats are deposited in a solid form at the bottom of the vessel. This is then taken from the vat and the essence carefully poured from the sediment.
The alcoholic extracts of the pomades or solutions of the aromatics are called essences or extracts (French, extraits); the solutions obtained from resins and balsams are usually termed tinctures.
While some extracts, owing to their strong odor, can be used only when diluted with alcohol, others are employed in perfumes as such. Pure extracts (extraits purs) are those containing only a single odor and are but rarely used as perfumes; the latter are usually mixtures of several, often a great many odors.
[CHAPTER XI.]
DIRECTIONS FOR MAKING THE MOST IMPORTANT ESSENCES AND EXTRACTS.
Note.—There is considerable confusion, in works on perfumery, regarding the terms essence and extract. In French works, essence always means “essential oil.” Thus “essence de rose” is “essential oil of roses,” or “attar (otto) of roses.” Extrait (French) is used of alcoholic solutions of oils, as well as alcoholic extracts of pomades, or of substances not wholly soluble in alcohol, and also of compound liquids. In English, essence is used, and should be confined to alcoholic solutions of essential oils (“essence of lemon,” “essence of peppermint”). It is, then, equivalent to the term “spirit,” which is also used only of alcoholic solutions of essential oils or other volatile substance (such as: spirit of peppermint, essence of peppermint; spirit of camphor, etc.). Liquid alcoholic extracts of substances not wholly soluble in alcohol are properly called tinctures (for instance, tincture of benzoin, tincture of musk); and liquid alcoholic extracts of pomades, or compound odorous liquids, are best comprised under the general term extracts.
We shall employ the terms essence, extract, and tincture in the sense here explained.