B. Chemical Products used for the Preparation of Perfumes.

Among all the substances belonging under this head, there is one which plays a prominent part in the manufacture of most perfumes. In handkerchief perfumes it is one of the most important substances, as it forms not only the greatest bulk, but the perfection of the perfume depends upon its quality. This substance is—

Alcohol,

also called spirit of wine; French, esprit de vin; the well-known combustible liquid formed by the alcoholic fermentation of sugar, which is made on a large scale in extensive distilleries. Alcohol is a thin, mobile liquid with an aromatic odor. The usual “strong” alcohol of the market contains about ninety-four per cent of absolute alcohol by volume. This has a specific gravity of 0·820. Its boiling-point is 78·2° C. (172·40 F.), and it congeals at a very low temperature, below -100° C. Alcohol possesses great solvent power for resins, balsams, and essential oils.

These properties, however, belong only to the commercial stronger or so-called “druggists’ alcohol,” and more particularly to a very pure quality of it, as free as possible from fusel-oil compounds, known as cologne spirit. As absolute alcohol is also necessary for the purposes of perfumery, we shall briefly describe its preparation.

In order to make absolute alcohol, sulphate of copper is heated in a retort until it has changed into a white powder. After the powder has cooled in the covered retort, it is at once introduced into a large glass bottle; over it is poured the strongest obtainable alcohol (96% Tralles) which must be free from fusel oil; then the bottle is closed air-tight and repeatedly shaken. The sulphate of copper which has lost its water of crystallization by the heat reabsorbs it from the alcohol and again becomes blue and crystalline. Generally four pounds of sulphate of copper are used for ten quarts of alcohol; when white burnt sulphate of copper after long contact with alcohol still remains white, the alcohol is proved to be practically anhydrous (it may still contain about two per cent of water).

Larger quantities of absolute alcohol are made in a copper still containing fused anhydrous chloride of calcium in small pieces. The apparatus is closed and alcohol of 94 to 95% is poured in through a tubulure. The mixture often grows so warm that the alcohol begins to pass over, so that but little heat need be applied to make the absolute alcohol distil over.

Absolute alcohol obtained in this way—for by repeated distillation we get at most an alcohol of 96%—abstracts water from the air with avidity; hence it must be preserved in air-tight vessels which should contain a small amount of anhydrous sulphate of copper.

Fig. 2.

Strong commercial alcohol contains varying amounts of water—from four to twenty parts by volume (96 to 80% alcohol); at the present time, however, it is always customary for dealers in this country to supply the officinal alcohol of 94%, when “strong alcohol” is called for. Its strength is measured by an areometer which sinks in proportion to the purity of the alcohol; the alcoholometer of Tralles or volumeter shows at once on its scale how many parts by volume of absolute alcohol (volume per cent) are contained in 100 volumes of alcohol. The adjoining figure (Fig. 2) shows Tralles’ alcoholometer, with the vessel in which the test is made. The readings of the instrument, however, are correct only at a temperature of 15·6° C. (60° F.), the so-called normal temperature; at a higher or lower point they must be corrected according to the tables appended.

At temperatures below the normal, the amount of alcohol is greater than the areometer indicates, hence a percentage must be added; at higher temperatures a percentage must be deducted.

Tables for Finding the True Percentage by Volume, at the Normal Temperature of 60° F., of Alcohol of Any Strength, when Tested at Temperatures Below or Above 60° F.

Table I.—For Temperatures Under 60° F.

Per cent
of
Alcohol
by
Volume.		Number of
F. Degrees
Requiring
Addition
of one to
Percentage.		Per cent
of
Alcohol
by
Volume.		Number of
F. Degrees
Requiring
Addition
of one to
Percentage.
215·4605·4
225·175615·4
234·725625·4
244·5635·625
254·5645·625
264·5655·625
274·5665·625
284·275675·625
294·275685·85
304·275695·85
314·275705·85
324·275715·85
334·275725·85
344·275735·85
354·5746·075
364·5756·075
374·5766·075
384·5776·075
394·5786·3
404·5796·3
414·725806·3
424·725816·525
434·725826·525
444·725836·75
454·95846·75
464·95856·75
474·95866·75
484·95876·975
494·95887·2
505·175897·425
515·175907·65
525·175917·875
535·175928·1
545·175938·325
555·175948·775
565·175959·
575·4969·45
585·49710·125
595·4

Explanation.—Supposing an alcohol should be found to contain 40 per cent of absolute alcohol by Tralles’ alcoholometer at 45° F. The difference between 45 and 60° F. is 15. Opposite to 40 will be found the figure 4·5. For every 4·5 degrees F. below 60° there must be added 1 to the alcoholic percentage. Hence for 15 degrees there must be added 3.3 degrees. The alcoholic percentage, by volume, therefore, is 43·3 per cent.

Table II.—For Temperatures Above 60° F.

Per cent
of
Alcohol
by
Volume.		Number of
F. Degrees
Requiring
Subtraction
of one to
Percentage.		Per cent
of
Alcohol
by
Volume.		Number of
F. Degrees
Requiring
Subtraction
of one to
Percentage.
215·85615·175
225·625625·175
235·4635·175
245·175645·175
254·95655·175
264·95665·4
274·725675·4
284·725685·4
294·5695·625
304·5705·625
314·5715·625
324·5725·625
334·5735·625
344·5745·625
354·5755·85
364·5765·85
374·5775·85
384·5785·85
394·5796·075
404·5806·075
414·5816·075
424·5826·075
434·5836·3
444·5846·3
454·5856·3
464·5866·525
474·725876·525
484·725886·525
494·725896·75
504·725906·975
514·725916·975
524·725927·425
534·95937·425
544·95947·65
554·95957·65
565·175968·1
575·175978·1
585·175988·325
595·175999·45
605·1751009.9

Explanation.—In this case, the same calculation is performed as directed under Table I., except that the correction is to be deducted instead of added.

Aside from the water present in it, commercial alcohol is never pure, but always contains small quantities, at times mere traces, of substances having a peculiar, sometimes pleasant, sometimes disagreeable, but invariably intense odor, which are known as fusel oils. The variety of fusel oil differs with the raw material from which the alcohol was made; there is a potato fusel oil (chemically amyl alcohol), a corn fusel oil, a beet fusel oil, wine fusel oil (œnanthic ether), etc. Fusel oils, being themselves odorous substances, exert an influence on the fragrance of the perfume; hence it is a general rule in perfumery to use only alcohol free from fusel oil; that is, such from which the fusel oil has been extracted as far as possible by means of fresh charcoal. So-called “Cologne Spirit” of the best quality is, as a rule, practically free from it.

Strange to say, some essential oils or aromatic substances in general, develop their finest odors only when the perfumes are prepared with an alcohol from a certain source. While the charcoal treatment removes almost all the fusel oil, the remaining traces suffice to act as odorous substances in the true sense of the term and to produce with other aromatic bodies a harmony of the odor which can never be reached by the use of another variety of alcohol. To give but a single instance we may state that all the citron odors known in perfumery develop the finest aroma only when dissolved in alcohol made from wine and the solution is then distilled. The world-renowned eau de Cologne is made in this way; the other aromatic substances contained in it are added to the distillate from the spirit of wine and the citron oils; any cologne made in another manner or with another alcohol has a less fine odor. While the citron odors require true spirit of wine for the development of their full aroma, other scents require beet or corn alcohol to bring out their best odor. Jasmine, tuberose, orange flowers, violet, etc., and all animal odors (ambergris, musk, and civet) belong to the latter class. For this remarkable and to the perfumer most important fact we know no other explanation than that traces of fusel oils present even in rectified alcohol take part in the general impression made on the olfactory nerves, acting as true aromatic substances.

Cologne spirit is expensive, but this should not be a reason for accepting a cheaper grade, with which it would be absolutely impossible to make really fine perfumes.

Alcohol is also generally used for the direct extraction of odorous substances from plants, as will be seen in the description of the processes employed in the preparation of the so-called essences or extracts. For these purposes, too, the best cologne spirit only should be used, that is, alcohol which has been freed from fusel oil and redistilled, for in no other way can the aromatic substances be obtained in the greatest possible purity. And this is indispensable for the preparation of really fine perfumes, for we do not hesitate to say that French and English perfumes have acquired their deserved reputation mainly through the great care exercised in the selection of their raw materials, and especially of the alcohol used for extraction.

Alloxan.

This preparation, which is used in making a fine skin cosmetic, is manufactured in chemical laboratories from uric acid heated with nitric acid. Alloxan is a crystalline colorless body which has the property of gradually producing a red tint on the skin and finds employment for this reason.

Ammonia.

Ammonia is a gas formed by the decomposition of nitrogenous substances, but chiefly obtained, on a large scale, from the so-called “gas liquor” of gas works. By itself it develops a very disagreeable odor and stimulates the lachrymal glands to secretion—a fact which can be verified in any stable. A solution of the gas (water of ammonia; liquor ammoniæ) possesses the same properties. In perfumery ammonia is never used alone, but only in combination with other odors, namely, in the manufacture of smelling salts (French: sels volatils; German: Riechsalze), which are much in favor in England and in this country. For the purposes of the perfumer, the greater part of the commercial ammonia is unsuitable owing to its tarry odor. Pure ammonia is best prepared by heating equal parts of quicklime and powdered sal-ammoniac in a retort, and conducting the generated gas into water which dissolves it with avidity, one quart of water dissolving more than seven hundred quarts of ammonia gas.

Carbonate of Ammonia,

a combination of ammonia with carbonic acid, occurs in commerce in large transparent lumps, often covered with a white dust of bicarbonate of ammonia, which in the air continually develop ammonia and therefore always smell of it. This commercial product is, as a rule, sufficiently pure to be used in perfumery; as to its application the same remarks apply as were made under the head of ammonia.

Oil of Bitter Almonds (Oleum Amygdalæ amaræ).

This is made from bitter almonds, previously deprived of fatty oil by pressure, which are mixed with an equal weight of water and set in a warm place. The amygdalin undergoes decomposition into sugar, hydrogen cyanide, and benzoyl hydride or oil of bitter almonds. After one or two days the mass is distilled; the distillate being a colorless liquid, containing, besides oil of bitter almonds, hydrogen cyanide or prussic acid, one of the most virulent poisons, from which it must be freed. This is done by shaking the liquid repeatedly with dilute solution of potassa, followed by agitation with water. Pure oil of bitter almonds is not poisonous, but has a very strong narcotic odor of bitter almonds, which, however, becomes most marked when largely diluted with water.

Benzoic Acid (Acidum benzoicum).

This acid, contained in benzoin, is made also synthetically from other materials, in chemical laboratories. When pure it forms needle-shaped crystals having a silky gloss; they have a peculiar acrid taste, but no odor. Synthetic benzoic acid is worthless to the perfumer; in his art he can use only a benzoic acid made from gum benzoin by sublimation, because it contains a very aromatic essential oil for which the acid is merely the vehicle and which can also be employed alone.

As this sublimed benzoic acid is often adulterated with the artificial, we advise the manufacturer of perfumery to make his own benzoic acid according to the following directions.

The Manufacture of Sublimed Benzoic Acid.

Fig. 3.

About four pounds of benzoin B of best quality is broken into small pieces and placed in a small copper boiler K (Fig. 3); over its entire surface is pasted white blotting paper L, and to this is pasted a cone of strong paper which must surround the edge of the boiler. The cone ends above in a paper tube R, about five feet long and an inch wide. The copper boiler is placed in a large clay pot T (a flower pot) and surrounded on all sides with fine sand. The clay pot is heated from without by a charcoal fire. After the pot has remained about half an hour on the fire, the latter is fanned to its utmost and kept at this point for thirty minutes. The heat volatilizes the benzoic acid, the above-mentioned essential oil, and some tarry substances of a brown color. The latter are arrested by the filter paper, while the benzoic acid is deposited on the cone and in the tube, in the form of delicate glossy needles which are very fragrant owing to the essential oil. The largest yield of benzoic acid is obtained when the temperature is raised very gradually, until finally nothing remains in the copper boiler but a brown, almost carbonized mass of a blistered appearance.

Borax (Sodii Boras)

is used in some preparations. Borax forms colorless crystals which slightly effloresce in dry air and hence must be preserved in tightly closed vessels. Reddish tinted crystals are contaminated with oxide of iron and should be rejected.

Permanganate of Potassium (Potassi Permanganas)

is a salt formed by fusing a mixture of manganese dioxide, potassa, and potassium chlorate, extracting the product with water, and evaporating the solution to crystallization; the salt is obtained in small dark violet, almost black crystals which dissolve in sixteen parts of water to which they impart a beautiful violet color. By contact with organic substances, or others easily oxidized, the solution changes its color into green and finally is decolorized, precipitating a brown powder. Owing to this change of color the salt has been called chameleon mineral. As its preparation requires considerable dexterity, it is preferable to buy it from reputable houses, rather than to make it. It is used in the manufacture of mouth washes and hair dyes. The solution of the salt causes brown stains on linen and the skin; they can be removed only if the spots are immediately washed with hydrochloric, oxalic, sulphuric, or another acid.

Acetic Acid (Acidum Aceticum).

Much confusion exists in the literature regarding the strength of acetic acid when merely called by this name. It is safe to assume that, in each country, the term applies to the acid officinal in its national pharmacopœia as “Acidum Aceticum.” Thus the Austrian and German pharmacopœias understand by it an acid containing 96% of absolute acetic acid, which is practically identical with what is known as glacial acetic acid. The latter is, in some pharmacopœias, distinguished by a special name: acidum aceticum glaciale, U.S. P.; acide acétique crystallisable, French Pharm.—In the present work, the author always intended the strong acid of the Austrian pharmacopœia to be understood when no other strength was designated. Like alcohol, strong acetic acid dissolves essential oils and is used in the manufacture of various toilet vinegars and washes. Acetic acid is made in chemical laboratories by distillation of acetate of sodium with sulphuric acid, or more commonly from wood vinegar. The buyer should always satisfy himself that the product is free from an empyreumatic odor which clings tenaciously to an insufficiently purified sample.

Fats.

Fats find extensive application in perfumery, in the preparation of the so-called huiles antiques, pomades, and many other cosmetics. They should be enumerated among the chemical products used in perfumery because they can never be employed in their commercial form, but must undergo some process of purification, which is effected less by mechanical than by chemical means. Commercial fats usually contain remnants of the animal or vegetable body from which they are derived: particles of blood and membranes occur frequently in animal fats; cell bodies and vegetable albumin in vegetable fats. Besides these mechanical impurities, fats, especially if old, sometimes contain small amounts of free fatty acids which suffice to impart to them the objectionable odor and taste peculiar to every rancid fat. While some fats, such as bear’s grease, butter of cacao, oil of sesame, and some others, remain free from rancidity for a long time, others undergo this change very rapidly; in fact, we may say that every fat which shows the slightest odor should be called rancid, for pure fat is absolutely odorless.

We shall here briefly describe the process employed in the fat industry and by perfumers for the purification of fats. Animal fat, such as lard, suet, bear’s grease, etc., as well as cocoanut and palm oils, are introduced into a large iron boiler containing dilute soda lye (not exceeding one per cent of caustic soda), and the lye is heated to boiling. In the boiler is a small pump terminating above in a curved tube having a rose of a watering-pot at the end. The pump is so arranged as to raise lye and melted fat at the same time and to return the fluid into the boiler in a fine spray. After the fat is melted, the solid matters floating on top are skimmed off with a perforated spoon, and then the pump is operated for about fifteen minutes. The contained shreds of membrane and similar substances are completely dissolved by the soda lye, the free fatty acids are perfectly combined, and the fat is at the same time decolorized. After cooling, it floats on the surface of the lye as a colorless and odorless fluid; it is ladled off and poured into tall tapering vessels which are well closed and preserved in cool cellars. Contact with the air, especially at higher temperatures, causes rancidity of the fat. For every twenty pounds of fat twenty quarts of lye are used.

According to another process the fat is purified by being heated with alum and table salt; or every twenty-five pounds of fat, one ounce of alum and two ounces of salt are dissolved in five gallons of water. The scum is carefully skimmed from the surface of the melted fat, and, after it has solidified, the fat is washed with water until the latter escapes perfectly tasteless and odorless.

The washing is a very complicated and tedious piece of work. Operating on a small scale, a slightly inclined marble slab is taken, upon which a thin stream of water is constantly falling from a tube arranged above it. The fat is placed on the slab in small quantities (not over two pounds) and ground with a muller, like oil colors, under a constant flow of water. Owing to the expense of hand labor, it is advisable to use a so-called vertical mill or chaser. This consists of a level, circular, horizontal marble slab, bearing a central, easily movable axis with a crosspiece upon which two, likewise vertical, cylindrical marble plates turn like wheels in a circle on the horizontal marble plate. The fat is placed on the latter and continually irrigated with water; behind every chaser is applied a marble plate with a blade which nearly touches the chasers and returns the fat displaced laterally, under the chasers. The axis around which the chasers run is kept moving by any available power, and the laborer has nothing to do but to replace the washed fat with crude.

Liquid fats are purified as follows:

The oil is intimately mixed with one per cent of sulphuric acid. The mixture assumes a black color, the vegetable mucilage present in the oil becoming carbonized. After several days’ rest the oil becomes clear and floats on the surface of the sulphuric acid which has assumed a black color from the presence of finely divided carbon. The oil is decanted and treated, in the manner above stated for solid fats, with caustic soda lye. Heating can be dispensed with if the pumping is continued for a longer time.

Benzoin and benzoic acid have the property of counteracting the tendency of fats to become rancid; it is advisable, therefore, to mix intimately with the completely washed fat a small amount of benzoic acid, at most one-one-thousandth part by weight.

The best way of preserving fats is by salicylic acid. This is added to solid fats while they are in a melted state; if oils, the acid is poured in and the bottle vigorously shaken. If the oil is in casks, a small bag filled with salicylic acid is hung into it from the bung-hole. The acid dissolves in the oil and is disseminated through it and thus effects its preservation. One-one-thousandth part by weight of the fat or oil is said to be more than sufficient to keep it perfectly fresh for years.

Fats differ largely in their physical properties—for instance, in their appearance, melting-point, firmness, etc. As we shall return to this subject in connection with the manufacture of some perfumes, it is enough here to state briefly that by the addition of spermaceti, wax, paraffin, etc., fats are made more transparent and firmer—a matter of importance for some cosmetic preparations.

Chinese Gelatin.

This substance, derived from several algæ, species of Eucheuma, indigenous to the Chinese sea, and identical with Japanese agar-agar, on being boiled with two hundred parts of water has the property of forming a colorless solution which solidifies on cooling. Owing to this property the addition of a small quantity of Chinese gelatin (0·1-0·2%) is an excellent means for imparting to certain pomades and ointments great transparency and firmness.

Fruit Ethers

are liquids which possess an agreeable, refreshing odor resembling that of some fruits. For this reason they are used in confectionery, in the manufacture of liqueurs, and also in many ways in perfumery. Chemically, fruit ethers are combinations of an organic acid—acetic, butyric, valerianic, etc.—with a so-called alcohol radicle such as ethyl and amyl. Their manufacture is connected with many difficulties and is but rarely attempted by perfumers, especially as these products are made a specialty in some chemical laboratories and are furnished at very low prices and of excellent quality. In perfumery the following fruit ethers are particularly employed.

Acetic Ether,

prepared by the distillation of acetate of sodium with alcohol and sulphuric acid, is a colorless liquid having an odor of fermenting apple juice, with a boiling-point at 74° C. (155° F.).

Pine-apple Ether

(ether or huile d’ananas) is made by the saponification of butter with solution of potassa, distillation of the soap with alcohol and sulphuric acid, and rectification of the distillate. It is an inflammable liquid with an intense odor of pine-apple; its boiling-point is 119° C. (246° F.). It is not generally used pure, as its odor needs some correction. This is accomplished by the addition of a little valerianate of amyl, and chloroform. Also in other ways.

Apple Ether,

prepared by distillation from valerianate of sodium with alcohol and sulphuric acid, and the subsequent addition of certain correctives (see below).

Pear Ether,

also called pear oil, chiefly valerianate of amyl oxide, can be obtained in large quantities from a by-product in the manufacture of potato spirit, namely, amyl alcohol, which is carefully heated in a still with bichromate of potassium and sulphuric acid. The product thus obtained has a very pleasant odor of fine pears and boils at 196° C. (385° F.). But the commercial “pear-essence” is a more complex body (see following table).

Nitrous Ether

is a very volatile liquid boiling at 16° C. (61° F.), which is obtained by distillation of strong alcohol with concentrated nitric acid and rectification of the distillate; it is less used in perfumery than the other fruit ethers.

Fruit ethers, owing to their low price and great strength, are frequently employed in the manufacture of cheap perfumery, in place of essential oils, but more largely for scenting soap.

The so-called raspberry and strawberry ethers consist of mixtures of acetic, pine-apple, apple, and other ethers (see following table), which, combined in certain proportions, really manifest an odor nearly akin to those of the fruits after which they are named.

Fruit Ethers (Fruit Essences).

Table Showing the Ingredients Usually Employed for Preparing Artificial Fruit Ethers (Fruit Essences).

A = Peach.I = Apple.
B = Apricot.J = Grape.
C = Plum.K = Gooseberry.
D = Cherry.L = Raspberry.
E = Black Cherry. M = Strawberry.
F = Lemon.N = Melon.
G = Pear.O = Pine-apple.
H = Orange.
ABCDEFGH IJKLMNO
Glycerin5483..51010 12........1
Chloroform..1......1..2 1....11....
Nitrous ether..........1.... 2211..21
Aldehyde2..5....2..2 1..555....
Acetate of ethyl5..55101055 ..2..111..
Formate of ethyl5..1........1 ......1545
Butyrate of ethyl5102........1 ..........5..
Valerianate of ethyl55............ ....11......
Benzoate of ethyl......55....1 ..1011......
Œnanthate of ethyl51412...... ..1..11....
Salicylate of methyl22..........1 ......1..10..
Sebacic acid1..........10.. ......13..10
Acetate of amyl..............10 10......2....
Butyrate of amyl..1......10.... ..............
Valerianate of amyl................ ....55......
Essence of orange..........10..10 15..........
Alcohol,
solutions
saturated in
the cold of		Tartaric acid........1....1 ....11......
Oxalic acid..1......1.... ..31........
Succinic acid......12...... ......1......
Benzoic acid................ ........1....