Slabbing.—This may be done mechanically by pushing the block of soap through a framework containing pianoforte wires fixed at equi-distances (Fig. 10, which shows a machine designed by E. Forshaw & Son, Ltd.), or the soap may be out by hand by pulling a looped wire through the mass horizontally along lines previously scribed, or, for a standard sized slab, the wire may be a fixture in a box-like arrangement, which is passed along the top of the soap, and the distance of the wire from the top of the box will be the thickness of the slab (Fig. 11).



All tallow soaps should be slabbed whilst still warm, cut into bars, and open-piled immediately; if this type of soap is cold when slabbed its appearance will be very much altered.

Barring.—The slabs are out transversely into bars by means of the looped wire, or more usually by a machine (Fig. 12), the lower framework of which, containing wires, is drawn through the soap placed on the base-board; the framework is raised, and the bars fall upon the shelf, ready for transference into piles. It has long been the custom in England to cut bars of soap 15 inches long, and weighing 3 lb. each, or 37-1/2 bars of soap to the cwt., but in recent years a demand has arisen for bars of so many various weights that it must be sometimes a difficult matter to know what sizes to stock.

In another type of barring machine, portions of the slab, previously cut to size, are pushed against a framework carrying wires, and the bars slide along a table ready for handling (Fig. 13).

In cutting machines, through which "washer" household soap is being passed, the bar is pushed at right angles through another frame containing wires, which divides it into tablets; these may be received upon racks and are ready for drying and stamping. It is needless to say that the slabs and tablets are cut with a view to reducing the amount of waste to the lowest possible limit. Such a machine, made by E. Forshaw & Son, Ltd., is shown in Fig. 14.



Open- and Close-piling.—As remarked previously, tallow soaps should be cut whilst warm, and the bars "open-piled," or stacked across each other in such a way that air has free access to each bar for a day. The bar of soap will skin or case-harden, and next day may be "close-piled," or placed in the storage bins, where they should remain for two or three weeks, when they will be in perfect condition for packing into boxes ready for distribution.



Drying.—"Oil soaps," as soaps of the washer type are termed, do not skin sufficiently by the open-piling treatment, and are generally exposed on racks to a current of hot air in a drying chamber in order to produce the skin, which prevents evaporation of water, and allows of an impression being given by the stamp without the soap adhering to the dies. It is of course understood that heavily liquored soaps are, as a rule, unsuitable for the drying treatment, as the bars become unshapely, and lose water rapidly.

Stamping.—Bar soaps are usually stamped by means of a hand-stamp containing removable or fixed brass letters (Fig. 15), with a certain brand or designation of quality and the name of the manufacturer or vendor, and are now ready for packing into boxes.

A very large bulk of the soap trade consists of the household quality in tablet form, readily divided into two cakes. These are stamped in the ordinary box moulds with two dies—top and bottom impressions—the die-plates, being removable, allow the impressions to be changed. This type of mould (Fig. 16) can be adjusted for the compression of tablets of varying thickness, the box preventing the escape of soap. We are indebted to E. Forshaw & Son, Ltd., for this illustration.



The stamping machine may be worked by hand (Fig. 17) or power driven. Where large quantities of a particular tablet have to be stamped, one of the many automatic mechanical stampers in existence may be employed, the tablets being conveyed to and from the dies by means of endless belts. Such a machine is shown in the accompanying illustration (Fig. 18).

If necessary, the soap is transferred to racks and exposed to the air, after which it is ready for wrapping, which is generally performed by manual labour, although in some instances automatic wrapping machines are in use.

Cardboard cartons are also used for encasing the wrapped tablets, the object being that these are more conveniently handled by tradesmen and may be advantageously used to form an attractive window display.

Cooling.—Many attempts have been made to shorten the time required for the framing and finishing of soap, by cooling the liquid soap as it leaves the pan.



With milling base, this is successfully accomplished in the Cressonnieres' plant, by allowing the hot soap to fall upon the periphery of a revolving drum which can be cooled internally by means of water.



In the case of household soaps, where the resultant product must be of good appearance and have a firm texture, the difficulty is to produce a bar fit for sale after the cooling has been performed, as soap which has been suddenly chilled lacks the appearance of that treated in the ordinary way. Several patents have been granted for various methods of moulding into bars in tubes, where the hot soap is cooled by being either surrounded by running water in a machine of similar construction to a candle machine, or rotated through a cooling medium; and numerous claims have been made both for mechanical appliances and for methods of removing or discharging the bars after cooling. In many instances these have proved unsatisfactory, owing to fracture of the crystalline structure. Moreover, in passing through some of the devices for solidification after chilling, the soap is churned by means of a worm or screw, and this interferes with the firmness of the finished bar, for, as is well known, soap which has been handled too much, does not regain its former firmness, and its appearance is rendered unsatisfactory.

A form of apparatus which is now giving satisfactory results is the Leimdoerfer continuous cooler (Fig. 19). This consists of a fixed charging hopper, A, a portable tank, B, containing tubes, and a detachable box, C, which can be raised or lowered by means of a screw, D. The bottom of the hopper is fitted with holes corresponding with the cooling tubes, e, and closed by plugs c, attached to a frame b, which terminates above in a screw spindle a, by means of which the frame and plugs can be raised and lowered so as to permit or stop the outflow of soap into the cooling tubes. The tubes are closed at the bottom by slides d, and the box B, in which they are mounted, is carried on a truck running on rails. The charging hopper can be connected with the soap-pan by a pipe, and when the hopper is filled with liquid soap the plugs c are raised and the air in the box C exhausted, thus causing the soap to descend into the cooling tubes.



The slides d are closed, the screw D released, and the box B moved away to make room for another. At the end of the rail track is an ejecting device which pushes the cooled soap out of the tubes, and the truck is run back on a side track to the machine for use over again. In this way the apparatus can be worked continuously, the soap being received from the cooling pipes on a suitable arrangement for transport to the press or store room.

A similar idea has been made the subject of a patent by Holoubek (Eng. Pat. 24,440, 1904, Fig. 20). The soap is run into frames or moulds having open sides, which are closed by being clamped with screws and pressure plates between cooling tubes through which water circulates.



CHAPTER VII.

TOILET, TEXTILE AND MISCELLANEOUS SOAPS.

Toilet Soaps—Cold Process Soaps—Settled Boiled Soaps—Remelted Soaps—Milled Soaps—Drying—Milling and Incorporating Colour, Perfume, or Medicament—Perfume—Colouring Matter—Neutralising and Superfatting Material—Compressing—Cutting—Stamping—Medicated Soaps—Ether Soap—Floating Soaps—Shaving Soaps—Textile Soaps—Soaps for Woollen, Cotton and Silk Industries—Patent Textile Soaps—Miscellaneous Soaps.

Toilet Soaps.—By the term "toilet soap" is inferred a soap specially adapted for toilet use by reason not only of its good detergent and lathering qualities, but also on account of its freedom from caustic alkali and any other ingredient likely to cause irritation or injury to the skin.

Toilet soaps may be simply classified according to their method of preparation into the following four classes:—

(1) Cold process soaps. (2) Settled boiled soaps. (3) Remelted soaps. (4) Milled soaps.

Soaps of the first class are of comparatively trifling importance, having been superseded by the other qualities. Details of the "cold process" have already been given on page 46; it is only necessary to add the desired perfume and colouring matter to the soap.

The second class consists of good quality settled soaps, direct from the copper, to which have been added, prior to framing, suitable perfume and colouring matter, also, if necessary, dealkalising materials.

The third class is represented by soaps made by the old English method of remelting, which are often termed "perfumers'," or "little pan" soaps. The soap-base or mixture of various kinds of soap is remelted in a steam-jacketed pan, or pan provided with steam coils, and agitated. The agitation must not be too vigorous or lengthy, or the soap will become aerated. When all the soap is molten, additions of pearl ash solution are made to give it a finer and smoother texture, render it more transparent, and increase its lathering properties. The necessary colour, in a soluble form, is well incorporated, and lastly the perfume. Owing to volatilisation, much of the perfume is lost when added to hot soap, and it is necessary to add a large quantity to get the desired odour; hence the cheaper essential oils have to be used, so that the perfume of this class of soap is not so delicate as that of milled soaps, although it is quite possible to produce remelted soaps as free from uncombined alkali as a milled toilet soap.

Palm-oil soap often forms the basis for yellow and brown toilet soaps of this class. The old-fashioned Brown Windsor soap was originally a curd soap that with age and frequent remelting had acquired a brown tint by oxidation of the fatty acids—the oftener remelted the better the resultant soap.

Medicaments are sometimes added to these soaps, e.g., camphor, borax, coal-tar, or carbolic. Oatmeal and bran have been recommended in combination with soap for toilet purposes, and a patent (Eng. Pat. 26,396, 1896) has been granted for the use of these substances together with wood-fibre impregnated with boric acid.

After cooling in small frames, the soap is slabbed, and cut into blocks, and finally into portions suitable for stamping in a press (hand or steam driven) with a design or lettering on each side.

Milled Toilet Soaps.—Practically all high-class soaps now on the market pass through the French or milling process. This treatment, as its name implies, was first practised by the French who introduced it to this country, and consists briefly of (i.) drying, (ii.) milling and incorporating colour, perfume or medicament, (iii.) compressing, and (iv.) cutting and stamping.

The advantages of milled soap over toilet soap produced by other methods are that the former, containing less water and more actual soap, is more economical in use, possesses a better appearance, and more elegant finish, does not shrink or lose its shape, is more uniform in composition, and essential oils and delicate perfumes may be incorporated without fear of loss or deterioration.

Only soap made from best quality fats is usually milled, a suitable base being that obtained by saponifying a blend of the finest white tallow with a proportion, not exceeding 25 per cent., of cocoa-nut oil, and prepared as described in Chapter V.

The first essential of a milling base is that the saponification should be thorough and complete; if this is not ensured, rancidity is liable to occur and a satisfactory toilet soap cannot be produced. The soap must not be short in texture or brittle and liable to split, but of a firm and somewhat plastic consistency.

(i.) Drying.—The milling-base, after solidification in the frames, contains almost invariably from 28 to 30 per cent. of water, and this quantity must be reduced to rather less than half before the soap can be satisfactorily milled. Cutting the soap into bars or strips and open piling greatly facilitates the drying, which is usually effected by chipping the soap and exposing it on trays to a current of hot air at 95-105 deg. F. (35-40 deg. C.).

There are several forms of drying chambers in which the trays of chips are placed upon a series of racks one above another, and warm air circulated through, and Fig. 21 shows a soap drying apparatus with fan made by W. J. Fraser & Co., Ltd., London.

The older method of heating the air by allowing it to pass over a pipe or flue through which the products of combustion from a coke or coal fire are proceeding under the floor of the drying chamber to a small shaft, has been superseded by steam heat. The air is either drawn or forced by means of quickly revolving fans through a cylinder placed in a horizontal position and containing steam coils, or passed over steam-pipes laid under the iron grating forming the floor of the chamber.



It will be readily understood that in the case of a bad conductor of heat, like soap-chippings, it is difficult to evaporate moisture without constantly moving them and exposing fresh surfaces to the action of heat.

In the Cressonnieres' system, where the shavings of chilled soap are dried by being carried through a heated chamber upon a series of endless bands (the first discharging the contents on to a lower belt which projects at the end, and is moving in the opposite direction, and so on), this is performed by intercepting milling rollers in the system of belts (Eng. Pat. 4,916, 1898) whereby the surfaces exposed to the drying are altered, and it is claimed that the formation of hardened crust is prevented.

In the ordinary methods of drying, the chips are frequently moved by hand to assist uniform evaporation.

The degree of saturation of the air with moisture must be taken into consideration in regulating the temperature and flow of air through the drying chamber, and for this purpose the use of a hygrometer is advantageous.

It is very important that the correct amount of moisture should be left in the soap, not too much, nor too little; the exact point can only be determined by judgment and experience, and depends to a considerable extent upon the nature of the soap, and also on the amount of perfume or medicament to be added, but speaking generally, a range of 11 to 14 per cent. gives good results. If the soap contains less than this amount it is liable to crumble during the milling, will not compress satisfactorily, and the finished tablet may have a tendency to crack and contain gritty particles so objectionable in use. If, on the other hand, the soap is left too moist, it is apt to stick to the rollers and mill with difficulty, and during compression the surface assumes a blistered and sticky appearance.

(ii.) Milling and Incorporation of Colour, Perfume or Medicament.—The object of milling is to render the soap perfectly homogeneous, and to reduce it to a state in which colour, perfume, or any necessary neutralising material or other substance may be thoroughly incorporated. The milling machine consists of smooth granite rollers, fitted with suitable gearing and working in an iron framework (Fig. 22). The rollers are connected in such a manner that they rotate at different speeds, and this increases the efficiency of the milling, and ensures that the action of the rollers is one of rubbing rather than crushing.

By means of suitably arranged screws the pressure of the rollers on one another can be adjusted to give the issuing soap any desired thickness; care should be taken that the sheets of soap are not unnecessarily thick or the colour and odour will not be uniform.

The soap, in the form of chips, is introduced on to the rollers through a hopper, and after one passage through the mill, from bottom to top, one of the serrated knife edges is applied and the ribbons of the soap are delivered into the top of the hopper where the colour, perfume, and any other desired admixture is added, and the milling operation repeated three or four times. When the incorporation is complete the other scraper is fixed against the top roller and the soap ribbon passed into the receptacle from which it is conveyed to the compressor. A better plan, however, especially in the case of the best grade soaps, where the perfumes added are necessarily more delicate and costly, is to make the addition of the perfume when the colour has been thoroughly mixed throughout the mass. Another method is to mill once and transfer the mass to a rotary mixing machine, fitted with internal blades, of a peculiar form, which revolve in opposite directions one within the other as the mixer is rotated. The perfume, colouring matter, etc., are added and the mixer closed and set in motion, when, after a short time, the soap is reduced to a fine granular condition, with the colour and perfume evenly distributed throughout the whole. By the use of such machines, the loss of perfume by evaporation, which during milling is quite appreciable, is reduced to a minimum, and the delicacy of the aroma is preserved unimpaired.



Prolonged milling, especially with a suitable soap base, tends to produce a semi-transparent appearance, which is admired by some, but the increased cost of production by the repeated milling is not accompanied by any real improvement in the soap.

Perfume.—The materials used in perfuming soap will be dealt with fully in the next chapter. The quantity necessary to be added varies considerably with the nature of the essential oils, and also the price at which the soap is intended to be sold. In the cheaper grades of milled soaps the quantity will range from 10-30 fluid ozs. per cwt., and but rarely exceeds 18-20 ozs., whereas in more costly soaps as much as 40-50 fluid ozs. are sometimes added to the cwt.

Colouring Matter.—During recent years an outcry has been made against highly coloured soaps, and the highest class soaps have been manufactured either colourless or at the most with only a very delicate tint. It is obvious that a white soap guarantees the use of only the highest grade oils and fats, and excludes the introduction of any rosin, and, so far, the desire for a white soap is doubtless justified. Many perfumes, however, tend to quickly discolour a soap, hence the advantage of giving it a slight tint. For this purpose a vegetable colouring matter is preferable, and chlorophyll is very suitable.



A demand still exists for brightly coloured soaps, and this is usually met by the use of coal-tar dyes. The quantity required is of course extremely small, so that no harm or disagreeable result could possibly arise from their use.

Neutralising and Superfatting Material.—If desired, the final neutralisation of free alkali can be carried out during the milling process, any superfatting material being added at the same time. The chief neutralising reagents have already been mentioned in Chapter VI.

With regard to superfatting material, the quantity of this should be very small, not exceeding 6-8 ozs. per cwt: The most suitable materials are vaseline, lanoline, or spermaceti.



(iii.) Compressing.—The next stage is the compression and binding of the soap ribbons into a solid bar suitable for stamping, and the plant used (Fig. 23) for this purpose is substantially the same in all factories. The soap is fed through a hopper into a strong metal conical-shaped tube like a cannon, which tapers towards the nozzle, and in which a single or twin screw is moving, and the soap is thereby forced through a perforated metallic disc, subjected to great pressure, and compressed. The screws must be kept uniformly covered with shavings during compression to obviate air bubbles in the soap.



The soap finally emerges through the nozzle (to which is attached a cutter of suitable shape and size according to the form it is intended the final tablet to take) as a long, polished, solid bar, which is cut with a knife or wire into lengths of 2 or 3 feet, and if of satisfactory appearance, is ready for cutting and stamping. The nozzle of the plodder is heated by means of a Bunsen burner to about 120 deg. or 130 deg. F. (49 deg.-55 deg. C.) to allow the soap to be easily forced out, and this also imparts a good gloss and finish to the ejected bar—if the nozzle is too hot, however, the soap will be blistered, whereas insufficient heat will result in streaky soap of a poor and dull appearance.

(iv.) Cutting and Stamping.—In cutting the soap into sections for stamping, the cutter should shape it somewhat similar to the required finished tablet.

Many manufacturers cut the soap into sections having concave ends, and in stamping, the corners are forced into the concavity, with the result that unsightly markings are produced at each end of the tablet. It is preferable to have a cutter with convex ends, and if the stamping is to be done in a pin mould the shape should be a trifle larger than the exact size of the desired tablet.



The stamping may be performed by a hand stamper (Fig. 24), a screw press (Fig. 25), or by a steam stamper. The screw press works very satisfactorily for toilet soaps.

There are two kinds of moulds in use for milled soaps:—

(a) Pin Moulds in which tablets of one size and shape only can be produced (Fig. 25). The edges of the mould meet very exactly, the upper part of the die carries two pins attached to the shoulder, and these are received into two holes in the shoulder of the bottom plate. The superfluous soap is forced out as the dies meet.

(b) Band or Collar Moulds.—In this form (Fig, 27) the mould may be adjusted to stamp various sized tablets, say from 2 ozs. to 5-1/3 ozs. and different impressions given by means of removable die plates. The band or collar prevents the soap squeezing out sideways. We are indebted to R. Forehaw & Son, Ltd., for the loan of this illustration.

It is usual to moisten the soap or mould with a dilute solution of glycerine if it should have a tendency to stick to the die plates.

The soap is then ready for final trimming, wrapping, and boxing.



MEDICATED SOAPS.

The inherent cleansing power of soap renders it invaluable in combating disease, while it also has distinct germicidal properties, a 2 per cent. solution proving fatal to B. coli communis in less than six hours, and even a 1 per cent. solution having a marked action on germs in fifteen minutes.

Many makers, however, seek more or less successfully to still further increase the value of soap in this direction by the incorporation of various drugs and chemicals; and the number of medicated soaps on the market is now very large. Such soaps may consist of either hard or soft soaps to which certain medicaments have been added, and can be roughly divided into two classes, (a) those which contain a specific for various definite diseases, the intention being that the remedy should be absorbed by the pores of the skin and thus penetrate the system, and (b) those impregnated with chemicals intended to act as antiseptics or germicides, or, generally, as disinfectants.

The preparation of medicinal soaps appears to have been first taken up in a scientific manner by Unna of Hamburg in 1886, who advocated the use of soap in preference to plasters as a vehicle for the application of certain remedies.

Theoretically, he considered a soap-stock made entirely from beef tallow the most suitable for the purpose, but in practice found that the best results were obtained by using a superfatted soap made from a blend of one part of olive oil with eight parts of beef tallow, saponified with a mixture of two parts of soda to one part of potash, sufficient fat being employed to leave an excess of 3 or 4 per cent. unsaponified. Recent researches have shown, however, that even if a superfatted soap-base is beneficial for the preparation of toilet soaps (a point which is open to doubt), it is quite inadmissible for the manufacture of germicidal and disinfectant soaps, the bactericidal efficiency of which is much restricted by the presence of free fat.

Many of the medicaments added to soaps require special methods of incorporation therein, as they otherwise react with the soap and decompose it, forming comparatively inert compounds. This applies particularly to salts of mercury, such as corrosive sublimate or mercuric chloride, and biniodide of mercury, both of which have very considerable germicidal power, and are consequently frequently added to soaps. If simply mixed with the soap in the mill, reaction very quickly takes place between the mercury salt and the soap, with formation of the insoluble mercury compounds of the fatty acids, a change which can be readily seen to occur in such a soap by the rapid development on keeping, of a dull slaty-green appearance. Numerous processes have been suggested, and in some cases patented, to overcome this difficulty. In the case of corrosive sublimate, Geissler suggested that the soap to which this reagent is to be added should contain an excess of fatty acids, and would thereby be rendered stable. This salt has also been incorporated with milled soap in a dry state in conjunction with ammonio-mercuric chloride, [beta]-naphthol, methyl salicylate, and eucalyptol. It is claimed that these bodies are present in an unchanged condition, and become active when the soap is added to water as in washing. Ehrhardt (Eng. Pat. 2,407, 1898) patented a method of making antiseptic mercury soap by using mercury albuminate—a combination of mercuric chloride and casein, which is soluble in alkali, and added to the soap in an alkaline solution.

With biniodide of mercury the interaction can be readily obviated by adding to the biniodide of mercury an equal weight of potassium iodide. This process, devised and patented by J. Thomson in 1886, has been worked since that time with extremely satisfactory results. Strengths of 1/2, 1, and 3 per cent. biniodide are sold, but owing to the readiness with which it is absorbed by the skin a soap containing more than 1/2 per cent. should only be used under medical advice.

A similar combination of bromide of mercury with potassium, sodium, or ammonium bromide has recently been patented by Cooke for admixture with liquid, hard, or soft soaps.

Zinc and other Metallic Salts.—At various times salts of metals other than mercury have been added to soap, but, owing to their insolubility in water, their efficiency as medicaments is very trifling or nil. Compounds have been formed of metallic oxides and other salts with oleic said, and mixtures made with vaseline and lanoline, and incorporated with soap, but they have not met with much success.

Another chemical commonly added to soap is Borax. In view of its alkaline reaction to litmus, turning red litmus blue, this salt is no doubt generally regarded as alkaline, and, as such, without action on soap. On the contrary, however, it is an acid salt containing an excess of boric acid over the soda present, hence when it is added to soap, fatty acids are necessarily liberated, causing the soap to quickly become rancid. As a remedy for this it has been proposed to add sufficient alkali to convert the borax into neutral mono-borate of soda which is then added to the soap. This process is patented and the name "Kastilis" has been given to the neutral salt. The incorporation of borax with the addition of gum tragasol forms the subject of two patents (Eng. Pats. 4,415, 1904; and 25,425, 1905); increased detergent and lasting properties are claimed for the soap. Another patented process (Eng. Pat. 17,218, 1904) consists of coating the borax with a protective layer of fat or wax before adding to the soap with the idea that reaction will not take place until required. Boric acid possesses the defects of borax in a greater degree, and would, of course, simply form sodium borate with liberation of fatty acids, so should never be added to a neutral soap.

Salicylic Acid is often recommended for certain skin diseases, and here again the addition of the acid to soap under ordinary conditions results in the formation of sodium salicylate and free fatty acids.

To overcome this a process has recently been patented for rubbing the acid up with vaseline before addition to soap, but the simplest way appears to be to add the soda salt of the acid to soap.

Amongst the more common milled medicated toilet soaps may be mentioned, in addition to the above:—

Birch Tar Soap, containing 5 or 10 per cent. birch tar, which has a characteristic pungent odour and is recommended as a remedy for eczema and psoriasis.

Carbolic Soap.—A toilet soap should not contain more than 3 per cent. of pure phenol, for with larger quantities irritation is likely to be experienced by susceptible skins.

Coal Tar.—These soaps contain, in addition to carbolic acid and its homologues, naphthalene and other hydrocarbons derived from coal, naphthol, bases, etc. Various blends of different fractions of coal tar are used, but the most valuable constituents from a disinfectant point of view are undoubtedly the phenols, or tar acids, though in this case as with carbolic and cresylic soaps, the amount of phenols should not exceed 3 per cent. in a toilet soap. An excess of naphthalene should also be avoided, since, on account of its strong odour, soaps containing much of it are unpopular. The odour of coal tar is considerably modified by and blends well with a perfume containing oils of cassia, lavender, spike, and red thyme.

Formaldehyde.—This substance is one of the most powerful disinfectants known, and it may be readily introduced into soap without undergoing any decomposition, by milling in 2-3 per cent. of formalin, a 40 per cent. aqueous solution of formaldehyde, which is a gas. White soaps containing this chemical retain their whiteness almost indefinitely.

New combinations of formaldehyde with other bodies are constantly being brought forward as disinfectants. Among others the compound resulting from heating lanoline with formaldehyde has been patented (Eng. Pat. 7,169, 1898), and is recommended as an antiseptic medicament for incorporation with soap.

Glycerine.—Nearly all soaps contain a small quantity of this body which is not separated in the lyes. In some cases, however, a much larger quantity is desired, up to some 6 or 8 per cent. To mill this in requires great care, otherwise the soap tends to blister during compression. The best way is to dry the soap somewhat further than usual, till it contains say only 9 or 10 per cent. moisture and then mill in the glycerine.

Ichthyol or Ammonium-Ichthyol-Sulphonate is prepared by treating with sulphuric acid, and afterwards with ammonia, the hydrocarbon oil containing sulphur obtained by the dry distillation of the fossil remains of fish and sea-animals, which form a bituminous mineral deposit in Germany. This product has been admixed with soap for many years, the quantity generally used being about 5 per cent.; the resultant soap is possessed of a characteristic empyreumatic smell, very dark colour, and is recommended for rosacea and various skin diseases, and also as an anti-rheumatic. Ichthyol has somewhat changed its character during recent years, being now almost completely soluble in water, and stronger in odour than formerly.

Iodine.—A soap containing iodine is sometimes used in scrofulous skin diseases. It should contain some 3 per cent. iodine, while potassium iodide should also be added to render the iodine soluble.

Lysol.—This name is applied to a soap solution of cresol, "Lysol Soap" being simply another form of coal-tar soap. The usual strength is 10 per cent. lysol, and constitutes a patented article (Fr. Pat. 359,061, 1905).

Naphthol.—[beta]-Naphthol, also a coal-tar derivative, is a good germicide, and, incorporated in soap to the extent of 3 per cent. together with sulphur, is recommended for scabies, eczema and many other cutaneous affections.

Sulphur.—Since sulphur is insoluble in water, its action when used in conjunction with soap can be but very slow and slight. Sulphur soaps are, however, very commonly sold, and 10 per cent. is the strength usually advocated, though many so-called sulphur soaps actually contain very little sulphur. They are said to be efficacious for acne and rosacea.

Sulphur soaps, when dissolved in water, gradually generate sulphuretted hydrogen, which, although characteristic, makes their use disagreeable and lessens their popular estimation.

Terebene.—The addition of this substance to soap, though imparting a very refreshing and pleasant odour, does not materially increase the disinfectant value of the soap. A suitable strength is 5 per cent.

Thymol.—This furnishes a not unpleasant, and very useful antiseptic soap, recommended especially for the cleansing of ulcerated wounds and restoring the skin to a healthy state. The normal strength is 3 per cent. It is preferable to replace part of the thymol with red thyme oil, the thymene of which imparts a sweeter odour to the soap than if produced with thymol alone. A suitable blend is 2-1/2 per cent. of thymol crystals and 1-1/2 per cent. of a good red thyme oil.

Of the vast number of less known proposed additions to toilet soaps, mention may be made in passing of:—

Fluorides.—These have been somewhat popular during recent years for the disinfection of breweries, etc., and also used to some extent as food preservatives. Of course only neutral fluorides are available for use in soap, acid fluorides and soap being obviously incompatible. In the authors' experience, however, sodium fluoride appears to have little value as a germicide when added to soap, such soaps being found to rapidly become rancid and change colour.

Albumen.—The use of albumen—egg, milk, and vegetable—in soap has been persistently advocated in this country during the past few years. The claims attributed to albumen are, that it neutralises free alkali, causes the soap to yield a more copious lather, and helps to bind it more closely, and a further inducement held out is that it allows more water to be left in the soap without affecting its firmness. Experiments made by the authors did not appear to justify any enthusiasm on the subject, and the use of albumen for soap-making in this country appears to be very slight, however popular it may be on the Continent. Numerous other substances have been proposed for addition to soaps, including yeast, tar from peat (sphagnol), Swedish wood tar, permanganate of potash, perborates and percarbonates of soda and ammonia, chlorine compounds, but none of these has at present come much into favour, and some had only ephemeral existence. Of the many drugs that it has been suggested to admix in soap for use in allaying an irritable condition of the skin, the majority are obviously better applied in the form of ointments, and we need not consider them further.

Ether Soap.—Another form of medicated soap made by a few firms is a liquid ether soap containing mercuric iodide, and intended for surgeons' use. This, as a rule, consists of a soap made from olive oil and potash, dissolved in alcohol and mixed with ether, the mercuric iodide being dissolved in a few drops of water containing an equal weight of potassium iodide, and this solution added to the alcohol-ether soap.

Floating Soaps.—Attempts have been made to produce tablets of soap that will float upon the surface of water, by inserting cork, or floats, or a metallic plate in such a manner that there is an air space between the metal and the soap. The more usual method is to incorporate into hot soap sufficient air, by means of a specially designed self-contained jacketed crutcher, in which two shafts carrying small blades or paddles rotate in opposite directions, to reduce the density of the soap below that of water and so enable the compressed tablet to float. The difference in weight of a tablet of the same size before and after aerating amounts to 10 per cent.

Ordinary milling soap is used as a basis for this soap; the settled soap direct from the copper at 170 deg. F. (77 deg. C.) is carefully neutralised with bicarbonate of sodium, oleic or stearic acids, or boro-glyceride, perfumed and aerated.

Floating soap, which is usually white (some are of a cream tint), cannot be recommended as economical, whilst its deficiency in lathering properties, owing to occluded air, is a serious drawback to its popularity as a toilet detergent.

Shaving Soaps.—The first essential of a shaving soap, apart from its freedom from caustic alkali or any substance exerting an irritating effect upon the skin, is the quick production of a profuse creamy lather which is lasting. Gum tragacanth is used in some cases to give lasting power or durability, but is not necessary, as this property is readily attained by the use of a suitable proportion of potash soap. The best shaving soaps are mixtures of various proportions of neutral soda and potash soaps, produced by the combination of ordinary milling base with a white potash soap, either melted or milled together. Glycerine is sometimes added, and is more satisfactorily milled in.

Every precaution should be taken to ensure thorough saponification of the soaps intended for blending in shaving soap, otherwise there will be a tendency to become discoloured and develop rancidity with age. Shaving soaps are delicately perfumed, and are placed on the market either in the form of sticks which are cut from the bar of soap as it leaves the compressor, or stamped in flat cakes.

Shaving creams and pastes are of the same nature as shaving soaps, but usually contain a larger proportion of superfatting material and considerably more water.

TEXTILE SOAPS.

In the woollen, cloth, and silk textile industries, the use of soap for detergent and emulsifying purposes is necessary in several of the processes, and the following is a brief description of the kinds of soap successfully employed in the various stages.

1. Woollen Industry.—The scouring of wool is the most important operation—it is the first treatment raw wool is subjected to, and if it is not performed in an efficient manner, gives rise to serious subsequent troubles to manufacturer, dyer, and finisher.

The object of scouring wool is to remove the wool-fat and wool perspiration (exuded from the skin of sheep), consisting of cholesterol and isocholesterol, and potassium salts of fatty acids, together with other salts, such as sulphates, chlorides, and phosphates. This is effected by washing in a warm dilute soap solution, containing in the case of low quality wool, a little carbonate of soda; the fatty matter is thereby emulsified and easily removed.

Soap, to be suitable for the purpose, must be free from uncombined caustic alkali, unsaponified fat, silicates, and rosin.

Wool can be dissolved in a moderately dilute solution of caustic soda, and the presence of this latter in soap, even in small quantities, is therefore liable to injure the fibres and make the resultant fabric possess a harsh "feel," and be devoid of lustre.

Unsaponified fat denotes badly made soap—besides reducing the emulsifying power of the liberated alkali, this fat may be absorbed by the fibres and not only induce rancidity but also cause trouble in dyeing.

Soaps containing silicates may have a deleterious action upon the fibres, causing them to become damaged and broken.

By general consent soaps containing rosin are unsuitable for use by woollen manufacturers, as they produce sticky insoluble lime and magnesia compounds which are deposited upon the fibres, and give rise to unevenness in the dyeing.

A neutral olive-oil soft soap is undoubtedly the best for the purpose of wool scouring, as, owing to its ready solubility in water, it quickly penetrates the fibres, is easily washed out, and produces a good "feel" so essential in the best goods, and tends to preserve the lustre and pliability of the fibre.

The high price of olive-oil soap, however, renders its use prohibitive for lower class goods, and in such cases no better soap can be suggested than the old-fashioned curd mottled or curd soaps (boiled very dry), as free as possible from uncombined caustic alkali. The raw wool, after this cleansing operation, is oiled with olive oil or oleine, prior to spinning; after spinning and weaving, the fabric, in the form of yarn or cloth, has to be scoured to free it from oil. The soap in most general use for scouring woollen fabrics is neutral oleine-soda soap. Some manufacturers prefer a cheap curd soap, such as is generally termed "second curd," and in cases where lower grades of wools are handled, the user is often willing to have soap containing rosin (owing to its cheapness) and considers a little alkalinity desirable to assist in removing the oil.

Another operation in which soap is used, is that of milling or fulling, whereby the fabric is made to shrink and thus becomes more compact and closer in texture. The fabric is thoroughly cleansed, for which purpose the soap should be neutral and free from rosin and silicates, otherwise a harsh feeling or stickiness will be produced. Curd soaps or finely-fitted soaps made from tallow or bleached palm oil, with or without the addition of cocoa-nut oil, give the best results. All traces of soap must be carefully removed if the fabric is to be dyed.

The woollen dyer uses soap on the dyed pieces to assist the milling, and finds that a good soap, made from either olive oil, bleached palm oil, or tallow, is preferable, and, although it is generally specified to be free from alkali, a little alkalinity is not of consequence, for the woollen goods are, as a rule, acid after dyeing, and this alkalinity would be instantly neutralised.

2. Cotton Industry.—Cotton fibres are unacted upon by caustic alkali, so that the soap used in cleaning and preparing cotton goods for dyeing need not be neutral, in fact alkalinity is a distinct advantage in order to assist the cleansing.

Any curd soap made from tallow, with or without the addition of a small quantity of cocoa-nut oil, may be advantageously used for removing the natural oil.

In cotton dyeing, additions of soap are often made to the bath, and in such cases the soap must be of good odour and neutral, lest the colours should be acted upon and tints altered. Soaps made from olive oil and palm oil are recommended. The same kind of soap is sometimes used for soaping the dyed cotton goods.

The calico-printer uses considerable quantities of soap for cleansing the printed-cloths. The soap not only cleanses by helping to remove the gummy and starchy constituents of the adhering printing paste, but also plays an important part in fixing and brightening the colours. Soaps intended for this class of work must be quite neutral (to obviate any possible alteration in colour by the action of free alkali), free from objectionable odour and rosin, and readily soluble in water. These qualities are possessed by olive-oil soaps, either soft or hard. A neutral olive-oil soft soap, owing to its solubility in cold water, may be used for fibres coloured with most delicate dyes, which would be fugitive in hot soap solutions, and this soap is employed for the most expensive work.

Olive-oil curd (soda) soaps are in general use; those made from palm oil are also recommended, although they are not so soluble as the olive-oil soaps. Tallow curd soaps are sometimes used, but the difficulty with which they dissolve is a drawback, and renders them somewhat unsuitable.

3. Silk Industry.—Silk is secured to remove the sericin or silk-glue and adhering matter from the raw silk, producing thereby lustre on the softened fibre and thus preparing it for the dyer.

The very best soap for the purpose is an olive-oil soft soap; olive-oil and oleine hard soaps may also be used. The soap is often used in conjunction with carbonate of soda to assist the removal of the sericin, but, whilst carbonates are permissible, it is necessary to avoid an excess of caustic soda.

Tallow soaps are so slowly soluble that they are not applicable to the scouring of silk.

The dyer of silk requires soap, which is neutral and of a pleasant odour. The preference is given to neutral olive-oil soft soap, but hard soaps (made from olive oil, oleine, or palm oil) are used chiefly on account of cheapness. It is essential, however, that the soap should be free from rosin on account of its frequent use and consequent decomposition in the acid dye bath, when any liberated rosin acids would cling to the silk fibres and produce disagreeable results.

Patent Textile Soaps.—Stockhausen (Eng. Pat. 24,868, 1897) makes special claim for a soap, termed Monopole Soap, to be used in place of Turkey-red oils in the dyeing and printing of cotton goods and finishing of textile fabrics. The soap is prepared by heating the sulphonated oil (obtained on treatment of castor oil with sulphuric acid) with alkali, and it is stated that the product is not precipitated when used in the dye-bath as is ordinary soap, nor is it deposited upon the fibres.

Another patent (Eng. Pat. 16,382, 1897), has for its object the obviating of the injurious effects upon wool, of alkali liberated from a solution of soap. It is proposed to accomplish this by sulphonating part of the fat used in making the soap.

Miscellaneous Soaps.—Under this heading may be classed soaps intended for special purposes and consisting essentially of ordinary boiled soap to which additions of various substances have been made.

With additions of naphtha, fractions of petroleum, and turpentine, the detergent power of the soap is increased by the action of these substances in removing grease.

Amongst the many other additions may be mentioned: ox-gall or derivatives therefrom (for carpet-cleaning soap), alkali sulphides (for use of lead-workers), aniline colours (for home-dyeing soaps), pumice and tripoli (motorists' soaps), pine-needle oil, in some instances together with lanoline (for massage soaps), pearl-ash (for soap intended to remove oil and tar stains), magnesia, rouge, ammonium carbonate, chalk (silversmiths' soap), powdered orris, precipitated chalk, magnesium carbonate (tooth soaps).

Soap powders or dry soaps are powdered mixtures of soap, soda ash, or soda crystals, and other chemicals, whilst polishing soaps often contain from 85 to 90 per cent. siliceous matter, and can scarcely be termed soap.



CHAPTER VIII.

SOAP PERFUMES.

Essential Oils—Source and Preparation—Properties—Artificial and Synthetic Perfumes.

The number of raw materials, both natural and artificial, at the disposal of the perfumer, has increased so enormously during recent years that the scenting of soaps has now become an art requiring very considerable skill, and a thorough knowledge of the products to be handled. Not only does the all-important question of odour come into consideration, but the action of the perfumes on the soap, and on each other, has also to be taken into account. Thus, many essential oils and synthetic perfumes cause the soap to darken rapidly on keeping, e.g., clove oil, cassia oil, heliotropin, vanillin. Further, some odoriferous substances, from their chemical nature, are incompatible with soap, and soon decompose any soap to which they are added, while in a few cases, the blending of two unsuitable perfumes results, by mutual reaction, in the effect of each being lost. In the case of oils like bergamot oil, the odour value of which depends chiefly on their ester content, it is very important that these should not be added to soaps containing much free alkali, as these esters are readily decomposed thereby. Some perfumes possess the property of helping the soap to retain other and more delicate odours considerably longer than would otherwise be possible. Such perfumes are known as "fixing agents" or "fixateurs," and among the most important of these may be mentioned musk, both natural and artificial, civet, the oils of Peru balsam, sandalwood, and patchouli, and benzyl benzoate.

The natural perfumes employed for addition to soaps are almost entirely of vegetable origin, and consist of essential oils, balsams, and resins, animal perfumes such as musk, civet, and ambergris being reserved principally for the preparation of "extraits".

As would be expected with products of such diverse character, the methods employed for the preparation of essential oils vary considerably. Broadly speaking, however, the processes may be divided into three classes—(1) expression, used for orange, lemon, and lime oils; (2) distillation, employed for otto of rose, geranium, sandalwood, and many other oils; and (3) extraction, including enfleurage, by which the volatile oil from the flowers is either first absorbed by a neutral fat such as lard, and then extracted therefrom by maceration in alcohol, or directly extracted from the flowers by means of a volatile solvent such as benzene, petroleum ether, or chloroform. The last process undoubtedly furnishes products most nearly resembling the natural floral odours, and is the only one which does not destroy the delicate fragrance of the violet and jasmine. The yield, however, is extremely small, and concrete perfumes prepared in this way are therefore somewhat costly.

The essential oils used are derived from upwards of twenty different botanical families, and are obtained from all parts of the world. Thus, from Africa we have geranium and clove oils; from America, bay, bois de rose, Canadian snake root, cedarwood, linaloe, peppermint, petitgrain, and sassafras; from Asia, camphor, cassia, cinnamon, patchouli, sandalwood, star anise, ylang-ylang, and the grass oils, viz., citronella, lemongrass, palmarosa, and vetivert; from Australia, eucalyptus; while in Europe there are the citrus oils, bergamot, lemon, and orange, produced by Sicily, aspic, lavender, neroli, petitgrain, and rosemary by France, caraway and clove by Holland, anise by Russia, and otto of rose by Bulgaria.

Attempts have been made to classify essential oils either on a botanical basis or according to their chemical composition, but neither method is very satisfactory, and, in describing the chief constituents and properties of the more important oils, we have preferred therefore to arrange them alphabetically, as being simpler for reference.

It is a matter of some difficulty to judge the purity of essential oils, not only because of their complex nature, but owing to the very great effect upon their properties produced by growing the plants in different soils and under varying climatic conditions, and still more to the highly scientific methods of adulteration adopted by unscrupulous vendors. The following figures will be found, however, to include all normal oils.

Anise Stell, or Star Anise, from the fruit of Illicium verum, obtained from China. Specific gravity at 15 deg. C., 0.980-0.990; optical rotation, faintly dextro- or laevo-rotatory, +0 deg. 30' to -2 deg.; refractive index at 20 deg. C., 1.553-1.555; solidifying point, 14 deg.-17 deg. C.; solubility in 90 per cent. alcohol, 1 in 3 or 4.

The chief constituents of the oil are anethol, methyl chavicol, d-pinene, l-phellandrene, and in older oils, the oxidation products of anethol, viz. anisic aldehyde and anisic acid. Since anethol is the most valuable constituent, and the solidifying point of the oil is roughly proportional to its anethol content, oils with a higher solidifying point are the best.

Aspic oil, from the flowers of Lavandula spica, obtained from France and Spain, and extensively employed in perfuming household and cheap toilet soaps; also frequently found as an adulterant in lavender oil. Specific gravity at 15 deg. C., 0.904-0.913; optical rotation, French, dextro-rotatory up to +4 deg., rarely up to +7 deg., Spanish, frequently slightly laevo-rotatory to -2 deg., or dextro-rotatory up to +7 deg.; esters, calculated as linalyl acetate, 2 to 6 per cent.; most oils are soluble in 65 per cent. alcohol 1 in 4, in no case should more than 2.5 volumes of 70 per cent. alcohol be required for solution.

The chief constituents of the oil are: linalol, cineol, borneol, terpineol, geraniol, pinene, camphene and camphor.

Bay oil, distilled from the leaves of Pimenta acris, and obtained from St. Thomas and other West Indian Islands. It is used to some extent as a perfume for shaving soaps, but chiefly in the Bay Rhum toilet preparation. Specific gravity at 15 deg. C., 0.965-0.980; optical rotation, slightly laevo-rotatory up to -3 deg.; phenols, estimated by absorption with 5 per cent. caustic potash solution, from 45 to 60 per cent.; the oil is generally insoluble in 90 per cent. alcohol, though when freshly distilled it dissolves in its own volume of alcohol of this strength.

The oil contains eugenol, myrcene, chavicol, methyl eugenol, methyl chavicol, phellandrene, and citral.

Bergamot oil, obtained by expression from the fresh peel of the fruit of Citrus Bergamia, and used very largely for the perfuming of toilet soaps. Specific gravity at 15 deg. C., 0.880-0.886; optical rotation, +10 deg. to +20 deg.; esters, calculated as linalyl acetate, 35-40 per cent., and occasionally as high as 42-43 per cent.; frequently soluble in 1.5 parts of 80 per cent. alcohol, or failing that, should dissolve in one volume of 82.5 or 85 per cent. alcohol. When evaporated on the water-bath the oil should not leave more than 5-6 per cent. residue.

Among the constituents of this oil are: linalyl acetate, limonene, dipentene, linalol, and bergaptene.

Bitter Almond Oil.—The volatile oil obtained from the fruit of Amygdalus communis. Specific gravity at 15 deg. C., 1.045-1.06; optically inactive; refractive index at 20 deg. C., 1.544-1.545; boiling point, 176-177 deg. C.; soluble in 1 or 1.5 volumes of 70 per cent. alcohol.

The oil consists almost entirely of benzaldehyde which may be estimated by absorption with a hot saturated solution of sodium bisulphite. The chief impurity is prussic acid, which is not always completely removed. This may be readily detected by adding to a small quantity of the oil two or three drops of caustic soda solution, and a few drops of ferrous sulphate solution containing ferric salt. After thoroughly shaking, acidulate with dilute hydrochloric acid, when a blue coloration will be produced if prussic acid is present.

The natural oil may frequently be differentiated from artificial benzaldehyde by the presence of chlorine in the latter. As there is now on the market, however, artificial oil free from chlorine, it is no longer possible, by chemical means, to distinguish with certainty between the natural and the artificial product. To test for chlorine in a sample, a small coil of filter paper, loosely rolled, is saturated with the oil, and burnt in a small porcelain dish, covered with an inverted beaker, the inside of which is moistened with distilled water. When the paper is burnt, the beaker is rinsed with water, filtered, and the filtrate tested for chloride with silver nitrate solution.

Canada snake root oil, from the root of Asarum canadense. Specific gravity at 15 deg. C., 0.940-0.962; optical rotation, slightly laevo-rotatory up to -4 deg.; refractive index at 20 deg. C., 1.485-1.490; saponification number, 100-115; soluble in 3 or 4 volumes of 70 per cent. alcohol.

The principal constituents of the oil are a terpene, asarol alcohol, another alcohol, and methyl eugenol. The oil is too expensive to be used in other than high-class toilet soaps.

Cananga or Kananga oil, the earlier distillate from the flowers of Cananga odorata, obtained chiefly from the Philippine Islands. Specific gravity at 15 deg. C., 0.910-0.940; optical rotation, -17 deg. to -30 deg.; refractive index at 20 deg. C., 1.4994-1.5024; esters, calculated as linalyl benzoate, 8-15 per cent.; soluble in 1.5 to 2 volumes of 95 per cent. alcohol, but becoming turbid on further addition.

The oil is qualitatively similar in composition to Ylang-Ylang oil, and contains linalyl benzoate and acetate, esters of geraniol, cadinene, and methyl ester of p-cresol.

Caraway oil, distilled from the seeds of Carum carui. Specific gravity at 15 deg. C., 0.907-0.915; optical rotation, +77 deg. to +79 deg.; refractive index at 20 deg. C., 1.485-1.486; soluble in 3 to 8 volumes of 80 per cent. alcohol. The oil should contain 50-60 per cent. of carvone, which is estimated by absorption with a saturated solution of neutral sodium sulphite. The remainder of the oil consists chiefly of limonene.

Cassia oil, distilled from the leaves of Cinnamomum cassia, and shipped to this country from China in lead receptacles. Specific gravity at 15 deg. C., 1.060-1.068; optical rotation, slightly dextro-rotatory up to +3 deg. 30'; refractive index at 20 deg. C., 1.6014-1.6048; soluble in 3 volumes of 70 per cent. alcohol as a general rule, but occasionally requires 1 to 2 volumes of 80 per cent. alcohol.

The value of the oil depends upon its aldehyde content, the chief constituent being cinnamic aldehyde. This is determined by absorption with a hot saturated solution of sodium bisulphite. Three grades are usually offered, the best containing 80-85 per cent. aldehydes, the second quality, 75-80 per cent., and the lowest grade, 70-75 per cent.

Other constituents of the oil are cinnamyl acetate and cinnamic acid. This oil gives the characteristic odour to Brown Windsor soap, and is useful for sweetening coal-tar medicated soaps.

Cedarwood oil, distilled from the wood of Juniperus virginiana. Specific gravity at 15 deg. C., 0.938-0.960; optical rotation, -35 deg. to -45 deg.; refractive index at 20 deg. C., 1.5013-1.5030. The principal constituents are cedrene and cedrol.

Cinnamon oil, distilled from the bark of Cinnamomum zeylanicum. Specific gravity at 15 deg. C., 1.00-1.035; optical rotation, laevo-rotatory up to -2 deg.; usually soluble in 2 to 3 volumes of 70 per cent. alcohol, but sometimes requires 1 volume of 80 per cent. alcohol for solution; aldehydes, by absorption with sodium bisulphite solution, 55-75 per cent.; and phenols, as measured by absorption with 5 per cent. potash, not exceeding 12 per cent.

The value of this oil is not determined entirely by its aldehyde content as is the case with cassia oil, and any oil containing more than 75 per cent. aldehydes must be regarded with suspicion, being probably admixed with either cassia oil or artificial cinnamic aldehyde. The addition of cinnamon leaf oil which has a specific gravity at 15 deg. C. of 1.044-1.065 is detected by causing a material rise in the proportion of phenols. Besides cinnamic aldehyde the oil contains eugenol and phellandrene.

Citronella Oil.—This oil is distilled from two distinct Andropogon grasses, the Lana Batu and the Maha pangiri, the former being the source of the bulk of Ceylon oil, and the latter being cultivated in the Straits Settlements and Java. The oils from these three localities show well-defined chemical differences.

Ceylon Citronella oil has the specific gravity at 15 deg. C., 0.900-0.920; optical rotation, laevo-rotatory up to -12 deg.; refractive index at 20 deg. C., 1.480-1.484; soluble in 1 volume of 80 per cent. alcohol; total acetylisable constituents, calculated as geraniol, 54-70 per cent.

Singapore Citronella Oil.—Specific gravity at 15 deg. C., 0.890-0.899; optical rotation, usually slightly laevo-rotatory up to -3 deg.; refractive index at 20 deg. C., 1.467-1.471; soluble in 1 to 1.5 volumes of 80 per cent. alcohol; total acetylisable constituents, calculated as geraniol, 80-90 per cent.

Java Citronella Oil.—Specific gravity at 15 deg. C., 0.890-0.901; optical rotation, -1 deg. to -6 deg.; total acetylisable constituents, calculated as geraniol, 75-90 per cent.; soluble in 1-2 volumes of 80 per cent. alcohol.

The chief constituents of the oil are geraniol, citronellal, linalol, borneol, methyl eugenol, camphene, limonene, and dipentene. It is very largely used for perfuming cheap soaps, and also serves as a source for the production of geraniol.

Bois de Rose Femelle oil, or Cayenne linaloe oil, distilled from wood of trees of the Burseraceae species. Specific gravity at 15 deg. C., 0.874-0.880; optical rotation, -11 deg. 30' to -16 deg.; refractive index at 20 deg. C., 1.4608-1.4630; soluble in 1.5 to 2 volumes of 70 per cent. alcohol.

The oil consists almost entirely of linalol, with traces of saponifiable bodies, but appears to be free from methyl heptenone, found by Barbier and Bouveault in Mexican linaloe oil. This oil is distinctly finer in odour than the Mexican product.

Clove oil, distilled from the unripe blossoms of Eugenia caryophyllata, the chief source of which is East Africa (Zanzibar and Pemba). Specific gravity at 15 deg. C., 1.045-1.061; optical rotation, slightly laevo-rotatory up to -1 deg. 30'; phenols, estimated by absorption with 5 per cent. potash solution, 86-92 per cent.; refractive index at 20 deg. C., 1.5300-1.5360; soluble in 1 to 2 volumes of 70 per cent. alcohol.

The principal constituent of the oil is eugenol, together with caryophyllene and acet-eugenol. While within certain limits the value of this oil is determined by its eugenol content, oils containing more than 93 per cent. phenols are usually less satisfactory in odour, the high proportion of phenols being obtained at the expense of the decomposition of some of the sesquiterpene. Oils with less than 88 per cent. phenols will be found somewhat weak in odour. This oil is extensively used in the cheaper toilet soaps and is an important constituent of carnation soaps. As already mentioned, however, it causes the soap to darken in colour somewhat rapidly, and must not therefore be used in any quantity, except in coloured soaps.

Concrete orris oil, a waxy substance obtained by steam distillation of Florentine orris root.

Melting point, 35-45 deg. C., usually 40-45 deg. C.; free acidity, calculated as myristic acid, 50-80 per cent.; ester, calculated as combined myristic acid, 4-10 per cent.

The greater part of the product consists of the inodorous myristic acid, the chief odour-bearing constituent being irone. The high price of the oil renders its use only possible in the very best quality soaps.

Eucalyptus Oil.—Though there are some hundred or more different oils belonging to this class, only two are of much importance to the soap-maker. These are:—

(i.) Eucalyptus citriodora. Specific gravity at 15 deg. C., 0.870-0.905; optical rotation, slightly dextro-rotatory up to +2 deg.; soluble in 4-5 volumes of 70 per cent. alcohol.

The oil consists almost entirely of citronellic aldehyde, and on absorption with saturated solution of sodium bisulphite should leave very little oil unabsorbed.

(ii.) Eucalyptus globulus, the oil used in pharmacy, and containing 50-65 per cent. cineol. Specific gravity at 15 deg. C., 0.910-0.930; optical rotation, +1 deg. to +10 deg.; soluble in 2 to 3 parts of 70 per cent. alcohol; cineol (estimated by combination with phosphoric acid, pressing, decomposing with hot water, and measuring the liberated cineol), not less than 50 per cent. Besides cineol, the oil contains d-pinene, and valeric, butyric, and caproic aldehydes. It is chiefly used in medicated soaps.

Fennel (sweet) oil, obtained from the fruit of Foeniculum vulgare, grown in Germany, Roumania, and other parts of Europe. Specific gravity at 15 deg. C., 0.965-0.985; optical rotation, +6 deg. to +25 deg.; refractive index at 20 deg. C., 1.515-1.548; usually soluble in 2-6 parts 80 per cent. alcohol, but occasionally requires 1 part of 90 per cent. alcohol.

The chief constituents of the oil are anethol, fenchone, d-pinene, and dipentene.

Geranium oils, distilled from plants of the Pelargonium species. There are three principal kinds of this oil on the market—the African, obtained from Algeria and the neighbourhood, the Bourbon, distilled principally in the Island of Reunion, and the Spanish. The oil is also distilled from plants grown in the South of France, but this oil is not much used by soap-makers. A specially fine article is sold by a few essential oil firms under the name of "Geranium-sur-Rose," which as its name implies, is supposed to be geranium oil distilled over roses. This is particularly suitable for use in high-class soaps. The following are the general properties of these oils. It will be seen that the limits for the figures overlap to a considerable extent.

_______________ African. Bourbon. Spanish. French. _____ ___ ___ ___ ___ Specific gravity at 15 deg. C. .890-.900 .888-.895 .895-.898 .897-.900 Optical rotation. -6 to -10 deg. -9 to -18 deg. -8 to -11 deg. -8 to -11 deg. Esters, calculated as 20-27 27-32 20-27 18-23 geranyl tiglate per cent. per cent. per cent. per cent. Total alcohols, as 68-75 70-80 65-75 66-75 geraniol. per cent. per cent. per cent. per cent. Solubility in 70 per cent. alcohol. 1 in 1.5-2 1 in 1.5-2 1 in 2-3 1 in 1.5-2 _____ ___ ___ ___ ___

The oil contains geraniol and citronellol, both free, and combined with tiglic, valeric, butyric, and acetic acids; also l-menthone. The African and Bourbon varieties are the two most commonly used for soap-perfurmery, the Spanish oil being too costly for extensive use.

Ginger-grass oil, formerly regarded as an inferior kind of palma-rosa but now stated to be from an entirely different source. Specific gravity at 15 deg. C., 0.889-0.897; optical rotation, +15 deg.

The oil contains a large amount of geraniol, together with di-hydrocumin alcohol, d-phellandrene, d-limonene, dipentene, and l-carvone.

Guaiac wood oil, distilled from the wood of Bulnesia sarmienti. Specific gravity at 30 deg. C., 0.967-0.975; optical rotation, -4 deg. 30' to -7 deg.; refractive index at 20 deg. C., 1.506-1.507; soluble in 3 to 5 volumes of 70 per cent. alcohol.

The principal constituent of the oil is guaiac alcohol, or gusiol. This oil, which has what is generally termed a "tea-rose odour," is occasionally used as an adulterant for otto of rose.

Lavender oil, distilled from the flowers of Lavandula vera, grown in England, France, Italy and Spain. The English oil is considerably the most expensive, and is seldom, if ever, used in soap. The French and Italian oils are the most common, the Spanish oil being a comparatively new article, of doubtful botanical origin, and more closely resembling aspic oil.

English Oil.—Specific gravity at 15 deg. C., 0.883-0.900; optical rotation, -4 deg. to -10 deg.; esters, calculated as linalyl acetate, 5-10 per cent.; soluble in 3 volumes of 70 per cent. alcohol.

French and Italian Oils.—Specific gravity at 15 deg. C., 0.885-0.900; optical rotation, -2 deg. to -9 deg.; refractive index at 20 deg. C., 1.459-1.464; esters, calculated as linalyl acetate, 20-40 per cent., occasionally higher; soluble in 1.5-3 volumes of 70 per cent. alcohol.

There was at one time a theory that the higher the proportion of ester the better the oil, but this theory has now to a very large extent become discredited, and there is no doubt that some of the finest oils contain less than 30 per cent. of esters.

Spanish Oil.—Specific gravity at 15 deg. C., 0.900-0.915; optical rotation, -2 deg. to +7 deg.; esters, calculated as linalyl acetate, 2-6 per cent.; soluble in 1-2 volumes of 70 per cent. alcohol.

The chief constituents of lavender oil are linalyl acetate, linalol, geraniol, and linalyl butyrate, while the English oil also contains a distinct amount of cineol.

Lemon oil, prepared by expressing the peel of the nearly ripe fruit of Citrus limonum, and obtained almost entirely from Sicily and Southern Italy. Specific gravity at 15 deg. C., 0.856-0.860; optical rotation, +58 deg. to +63 deg.; refractive index at 20 deg. C., 1.4730-1.4750; aldehydes (citral), 2.5 to 4 per cent.

The principal constituents of the oil are limonene and citral, together with small quantities of pinene, phellandrene, octyl and nonyl aldehydes, citronellal, geraniol, geranyl acetate, and the stearopten, citraptene.

Lemon-grass (so-called verbena) oil, distilled from the grass Andropogon citratus, which is grown in India and, more recently, in the West Indies. The oils from these two sources differ somewhat in their properties, and also in value, the former being preferred on account of its greater solubility in alcohol.

East Indian.—Specific gravity at 15 deg. C., 0.898-0.906; optical rotation, -0 deg. 30' to -6 deg.; aldehydes, by absorption with bisulphite of soda solution, 65 to 78 per cent.; refractive index at 20 deg. C., 1.485-1.487; soluble in 2-3 volumes of 70 per cent. alcohol.

West Indian.—Specific gravity at 15 deg. C., 0.886-0.893; optical rotation, faintly laevo-gyrate; refractive index at 20 deg. C., 1.4855-1.4876; soluble in 0.5 volume of 90 per cent. alcohol.

Lime oil, obtained by expression or distillation of the peel of the fruit of Citrus medica, and produced principally in the West Indies.

Expressed Oil.—Specific gravity at 15 deg. C., 0.870-0.885; optical rotation, +38 deg. to +50 deg. Its most important constituent is citral.

Distilled Oil.—This is entirely different in character to the expressed oil. Its specific gravity at 15 deg. C. is 0.854-0.870; optical rotation, +38 deg. to +54 deg.; soluble in 5-8 volumes of 90 per cent. alcohol.

Linaloe oil, distilled from the wood of trees of the Burseraceae family, and obtained from Mexico. Specific gravity at 15 deg. C., 0.876-0.892; optical rotation, usually laevo-rotatory, -3 deg. to -13 deg., but occasionally dextro-rotatory up to +5 deg. 30'; esters, calculated as linalyl acetate, 1-8 per cent.; total alcohols as linalol, determined by acetylation, 54-66 per cent.; soluble in 1-2 volumes of 70 per cent. alcohol.

This oil consists mainly of linalol, together with small quantities of methyl heptenone, geraniol, and d-terpineol.

Marjoram oil, distilled from Origanum majoranoides, and obtained entirely from Cyprus. Specific gravity at 15 deg. C., 0.966; phenols, chiefly carvacrol, estimated by absorption with 5 per cent. caustic potash solution, 80-82 per cent.; soluble in 2-3 volumes of 70 per cent. alcohol.

This oil is used in soap occasionally in place of red thyme oil.

Neroli Bigarade oil, distilled from the fresh blossoms of the bitter orange, Citrus bigaradia. Specific gravity at 15 deg. C., 0.875-0.882; optical rotation, +0 deg. 40' to +10 deg., and occasionally much higher; refractive index at 20 deg. C., 1.468-1.470; esters, calculated as linalyl acetate, 10-18 per cent.; soluble in 0.75-1.75 volumes of 80 per cent. alcohol, becoming turbid on further addition of alcohol.

The chief constituents of the oil are limonene, linalol, linalyl acetate, geraniol, methyl anthranilate, indol, and neroli camphor.

Orange (sweet) oil, expressed from the peel of Citrus aurantium. Specific gravity at 15 deg. C., 0.849-0.852; optical rotation, +95 deg. to +99 deg.; refractive index at 20 deg. C., 1.4726-1.4732.

The oil contains some 90 per cent. limonene, together with nonyl alcohol, d-linalol, d-terpineol, citral, citronellal, decyl aldehyde, and methyl anthranilate.

Palmarosa, or East Indian geranium oil, distilled from Andropogon Schoenanthus, a grass widely grown in India. Specific gravity at 15 deg. C., 0.888-0.895; optical rotation, +1 deg. to -3 deg.; refractive index at 20 deg. C., 1.472-1.476; esters, calculated as linalyl acetate, 7-14 per cent.; total alcohols, as geraniol, 75-93 per cent.; solubility in 70 per cent. alcohol, 1 in 3.

The oil consists chiefly of geraniol, free, and combined with acetic and caproic acids, and dipentene. It is largely used in cheap toilet soaps, particularly in rose soaps. It is also a favourite adulterant for otto of rose, and is used as a source of geraniol.

Patchouli oil, distilled from the leaves of Pogostemon patchouli, a herb grown in India and the Straits Settlements. Specific gravity at 15 deg. C., 0.965-0.990; optical rotation, -45 deg. to -63 deg.; refractive index at 20 deg. C., 1.504-1.511; saponification number, up to 12; sometimes soluble in 0.5 to 1 volume of 90 per cent. alcohol, becoming turbid on further addition. The solubility of the oil in alcohol increases with age. The oil consists to the extent of 97 per cent. of patchouliol and cadinene, which have little influence on its odour, and the bodies responsible for its persistent and characteristic odour have not yet been isolated.

Peppermint oil, distilled from herbs of the Mentha family, the European and American from Mentha piperita, and the Japanese being generally supposed to be obtained from Mentha arvensis. The locality in which the herb is grown has a considerable influence on the resulting oil, as the following figures show:—

English.—Specific gravity at 15 deg. C., 0.900-0.910; optical rotation, -22 deg. to -33 deg.; total menthol, 55-66 per cent.; free menthol, 50-60 per cent.; soluble in 3-5 volumes of 70 per cent. alcohol.

American.—Specific gravity at 15 deg. C., 0.906-0.920; optical rotation, -20 deg. to -33 deg.; total menthol, 50-60 per cent.; free menthol, 40-50 per cent. The Michigan oil is soluble in 3-5 volumes of 70 per cent. alcohol, but the better Wayne County oil usually requires 1-2 volumes of 80 per cent. alcohol, and occasionally 0.5 volume of 90 per cent. alcohol.

French.—Specific gravity at 15 deg. C., 0.917-0.925; optical rotation, -6 deg. to -10 deg.; total menthol, 45-55 per cent.; free menthol, 35-45 per cent.; soluble in 1 to 1.5 volumes of 80 per cent.

Japanese.—Specific gravity at 25 deg. C., 0.895-0.900; optical rotation, laevo-rotatory up to -43 deg.; solidifies at 17 to 27 deg. C.; total menthol, 70-90 per cent., of which 65-85 per cent. is free; soluble in 3-5 volumes of 70 per cent. alcohol.

The dementholised oil is fluid at ordinary temperatures, has a specific gravity of 0.900-0.906 at 15 deg. C., and contains 50-60 per cent. total menthol.

Some twenty different constituents have been found in American peppermint oil, including menthol, menthone, menthyl acetate, cineol, amyl alcohol, pinene, l-limonene, phellandrene, dimethyl sulphide, menthyl isovalerianate, isovalerianic aldehyde, acetaldehyde, acetic acid, and isovalerianic acid.

Peru balsam oil, the oily portion (so-called "cinnamein") obtained from Peru balsam. Specific gravity at 15 deg. C., 1.100-1.107; optical rotation, slightly dextro-rotatory up to +2 deg.; refractive index at 20 deg. C., 1.569 to 1.576; ester, calculated as benzyl benzoate, 80-87 per cent.; soluble in 1 volume of 90 per cent. alcohol.

The oil consists chiefly of benzyl benzoate and cinnamate, together with styracin, or cinnamyl cinnamate, and a small quantity of free benzoic and cinnamic acids.

Petitgrain oil, obtained by distillation of the twigs and unripe fruit of Citrus bigaradia. There are two varieties of the oil, the French and the South American, the former being the more valuable. Specific gravity at 15 deg. C., 0.886-0.900; optical rotation, -3 deg. to +6 deg.; refractive index at 20 deg. C., 1.4604-1.4650; esters, calculated as linalyl acetate, 40-55 per cent., for the best qualities usually above 50 per cent.; soluble as a rule in 2-3 volumes of 70 per cent. alcohol, but occasionally requires 1-2 volumes of 80 per cent. alcohol.

Among its constituents are limonene, linalyl acetate, geraniol and geranyl acetate.

Pimento oil (allspice), distilled from the fruit of Pimenta officinalis, which is found in the West Indies and Central America. Specific gravity at 15 deg. C., 1.040-1.060; optical rotation, slightly laevo-rotatory up to -4 deg.; refractive index at 20 deg. C., 1.529-1.536; phenols, estimated by absorption with 5 per cent. potash solution, 68-86 per cent.; soluble in 1-2 volumes of 70 per cent. alcohol.

The oil contains eugenol, methyl eugenol, cineol, phellandrene, and caryophyllene.

Rose oil (otto of rose), distilled from the flowers of Rosa damascena, though occasionally the white roses (Rosa alba) are employed. The principal rose-growing district is in Bulgaria, but a small quantity of rose oil is prepared from roses grown in Anatolia, Asia Minor. An opinion as to the purity of otto of rose can only be arrived at after a very full chemical analysis, supplemented by critical examination of its odour by an expert. The following figures, however, will be found to include most oils which can be regarded as genuine. Specific gravity at 30 deg. C., 0.850-0.858; optical rotation at 30 deg. C., -1 deg. 30' to -3 deg.; refractive index at 20 deg. C., 1.4600-1.4645; saponification value, 7-11; solidifying point, 19-22 deg. C.; iodine number, 187-194; stearopten content, 14-20 per cent.; melting point of stearopten, about 32 deg. C.

A large number of constituents have been isolated from otto of rose, many of which are, however, only present in very small quantities. The most important are geraniol, citronellol, phenyl ethyl alcohol, together with nerol, linalol, citral, nonylic aldehyde, eugenol, a sesquiterpene alcohol, and the paraffin stearopten.

Rosemary oil, distilled from the herb Rosemarinus officinalis, and obtained from France, Dalmatia, and Spain. The herb is also grown in England, but the oil distilled therefrom is rarely met with in commerce. The properties of the oils vary with their source, and also with the parts of the plant distilled, distillation of the stalks as well as the leaves tending to reduce the specific gravity and borneol content, and increase the proportion of the laevo-rotatory constituent (laevo-pinene). The following figures may be taken as limits for pure oils:—

French and Dalmatian.—Specific gravity at 15 deg. C., 0.900-0.916; optical rotation, usually dextro-rotatory, up to +15 deg., but may occasionally be laevo-rotatory, especially if stalks have been distilled with the leaves; ester, calculated as bornyl acetate, 1-6 per cent.; total borneol, 12-18 per cent.; usually soluble in 1-2 volumes of 82.5 per cent. alcohol.

Spanish.—The properties of the Spanish oil are similar to the others, except that it is more frequently laevo-rotatory.

Rosemary oil contains pinene, camphene, cineol, borneol, and camphor.

Sandalwood oil, obtained by distillation of the wood of Santalum album (East Indian), Santalum cygnorum (West Australian), and Amyris balsamifera (West Indian). The oils obtained from these three different sources differ very considerably in value, the East Indian being by far the best.

East Indian.—Specific gravity at 15 deg. C., 0.975-0.980; optical rotation, -14 deg. to -20 deg.; refractive index at 20 deg. C., 1.5045-1.5060; santalol, 92-97 per cent.; usually soluble in 4-6 volumes of 70 per cent. alcohol, though, an old oil occasionally is insoluble in 70 per cent. alcohol.

West Australian.—Specific gravity at 15 deg. C., 0.950-0.968; optical rotation, +5 deg. to +7 deg.; alcohols, calculated as santalol, 73-75 per cent.; insoluble in 70 per cent. alcohol, but readily dissolves in 1-2 volumes of 80 per cent. alcohol.

West Indian.—Specific gravity at 15 deg. C., 0.948-0.967; optical rotation, +13 deg. 30' to +30 deg.; insoluble in 70 per cent. alcohol.

In addition to free santalol, the oil contains esters of santalol and santalal.

Sassafras oil, distilled from the bark of Sassafras officinalis, and obtained chiefly from America. Specific gravity at 15 deg. C., 1.06-1.08; optical rotation, +1 deg. 50' to +4 deg.; refractive index at 20 deg. C., 1.524-1.532; soluble in, 6-10 volumes of 85 per cent. alcohol, frequently soluble in 10-15 volumes of 80 per cent. alcohol.

The chief constituents are safrol, pinene, eugenol, camphor, and phellandrene. The removal of safrol, either intentionally or by accident, owing to cooling of the oil and consequent deposition of the safrol, is readily detected by the reduction of the specific gravity below 1.06.

Thyme oil, red and white, distilled from the green or dried herb, Thymus vulgaris, both French and Spanish oils being met with. These oils are entirely different in character.

French.—Specific gravity at 15 deg. C., 0.91-0.933; slightly laevo-rotatory up to -4 deg., but usually too dark to observe; phenols, by absorption with 10 per cent. aqueous caustic potash, 25-55 per cent.; refractive index at 20 deg. C., 1.490-1.500; soluble in 1-1.5 volumes of 80 per cent. alcohol.

Spanish.—Specific gravity at 15 deg. C., 0.955-0.966; optical rotation, slightly laevo-gyrate; phenols, 70-80 per cent.; refractive index at 20 deg. C.; 1.5088-1.5122; soluble in 2-3 volumes of 70 per cent. alcohol.

In addition to the phenols, thymol or carvacrol, these oils contain cymene, thymene and pinene.

The white thyme oil is produced by rectifying the red oil, which is generally effected at the expense of a considerable reduction in phenol content, and hence in real odour value of the oil.

Verbena Oil.—The oil usually sold under this name is really lemon-grass oil (which see supra). The true verbena oil or French verveine is, however, occasionally met with. This is distilled in France from the verbena officinalis, and has the following properties: Specific gravity at 15 deg. C., 0.891-0.898; optical rotation, slightly dextro- or laevo-rotatory; aldehydes, 70-75 per cent.; soluble in 2 volumes of 70 per cent. alcohol.

The oil contains citral.

Vetivert oil, distilled from the grass, Andropogon muricatus, or Cus Cus, and grown in the East Indies.

Specific gravity at 15 deg. C., 1.01-1.03; optical rotation, +20 deg. to +26 deg.; saponification number, 15-30; refractive index at 20 deg. C., 1.521-1.524; soluble in 2 volumes of 80 per cent. alcohol.

The price of this oil makes its use prohibitive except in the highest class soaps.

Wintergreen Oil.—There are two natural sources of this oil, the Gaultheria procumbens and the Betula lenta. Both oils consist almost entirely of methyl salicylate and are practically identical in properties, the chief difference being that the former has a slight laevo-rotation, while the latter is inactive.

Specific gravity at 15 deg. C., 1.180-1.187; optical rotation, Gaultheria oil, up to -1 deg., Betula oil, inactive; ester as methyl salicylate, at least 98 per cent.; refractive index at 20 deg. C., 1.5354-1.5364; soluble in 2-6 volumes of 70 per cent. alcohol.

Besides methyl salicylate, the oil contains triaconitane, an aldehyde or ketone, and an alcohol.

Ylang-ylang oil, distilled from the flowers of Cananga odorata, the chief sources being the Philippine Islands and Java. Specific gravity at 15 deg. C., 0.924-0.950; optical rotation, -30 deg. to -60 deg., and occasionally higher; refractive index at 20 deg. C., 1.496-1.512; ester, calculated as linalyl benzoate, 27-45 per cent., occasionally up to 50 per cent.; usually soluble in 1/2 volume of 90 per cent. alcohol.

The composition of the oil is qualitatively the same as that of Cananga oil, but it is considerably more expensive and therefore can only be used in the highest grade soaps.

Artificial and Synthetic Perfumes.

During the past few years the constitution of essential oils has been studied by a considerable number of chemists, and the composition of many oils has been so fully determined that very good imitations can often be made at cheaper prices than those of the genuine oils, rendering it possible to produce cheap soaps having perfumes which were formerly only possible in the more expensive article.

There is a considerable distinction, however, often lost sight of, between an artificial and a synthetic oil. An artificial oil may be produced by separating various constituents from certain natural oils, and so blending these, with or without the addition of other substances, as to produce a desired odour, the perfume being, at any rate in part, obtained from natural oils. A synthetic perfume, on the other hand, is entirely the product of the chemical laboratory, no natural oil or substance derived therefrom entering into its composition.

The following are among the most important bodies of this class:—

Amyl salicylate, the ester prepared from amyl alcohol and salicylic acid, sometimes known as "Orchidee" or "Trefle". This is much used for the production of a clover-scented soap. It has the specific gravity at 15 deg. C., 1.052-1.054; optical rotation, +1 deg. 16' to +1 deg. 40'; refractive index at 20 deg. C., 1.5056; and should contain not less than 97 per cent. ester, calculated as amyl salicylate.

Anisic aldehyde, or aubepine, prepared by oxidation of anethol, and possessing a pleasant, hawthorn odour. This has the specific gravity at 15 deg. C., 1.126; refractive index at 20 deg. C., 1.5693; is optically inactive, and dissolves readily in one volume of 70 per cent. alcohol.

Benzyl Acetate, the ester obtained from benzyl alcohol and acetic acid. This has a very strong and somewhat coarse, penetrating odour, distinctly resembling jasmine. Its specific gravity at 15 deg. C. is 1.062-1.065; refractive index at 20 deg. C., 1.5020; and it should contain at least 97-98 per cent. ester, calculated as benzyl acetate.

Citral, the aldehyde occurring largely in lemon-grass and verbena oils, also to a less extent in lemon and orange oils, and possessing an intense lemon-like odour. It has a specific gravity at 15 deg. C., 0.896-0.897, is optically inactive, and should be entirely absorbed by a hot saturated solution of sodium bisulphite.

Citronellal, an aldehyde possessing the characteristic odour of citronella oil, in which it occurs to the extent of about 20 per cent., and constituting considerably over 90 per cent. of eucalyptus citriodora oil. Its specific gravity at 15 deg. C. is 0.862; refractive index at 20 deg. C., 1.447; optical rotation, +8 deg. to +12 deg.; and it should be entirely absorbed by a hot saturated solution of sodium bisulphite.

Coumarin, a white crystalline product found in Tonka beans, and prepared synthetically from salicylic acid. It has an odour resembling new-mown hay, and melts at 67 deg. C.

Geraniol, a cyclic alcohol, occurring largely in geranium, palma-rosa, and citronella oils. Its specific gravity at 15 deg. C. is 0.883-0.885; refractive index at 20 deg. C., 1.4762-1.4770; it is optically inactive, and boils at 218 deg.-225 deg. C.

Heliotropin, which possesses the characteristic odour of heliotrope, is prepared artificially from safrol. It crystallises in small prisms melting at 86 deg. C.

Hyacinth.—Most of the articles sold under this name are secret blends of the different makers. Styrolene has an odour very much resembling hyacinth, and probably forms the basis of most of these preparations, together with terpineol, and other artificial bodies. The properties of the oil vary considerably for different makes.

Ionone, a ketone first prepared by Tiemann, and having when diluted a pronounced violet odour. It is prepared by treating a mixture of citral and acetone with barium hydrate, and distilling in vacuo. Two isomeric ketones, [alpha]-ionone and [beta]-ionone, are produced, the article of commerce being usually a mixture of both. The two ketones have the following properties:—

Alpha-ionone.—Specific gravity at 15 deg. C., 0.9338; refractive index at 16.5 C., 1.50048 (Chuit); optically it is inactive.

Beta-ionone.—Specific gravity at 15 deg. C., 0.9488; refractive index at 16.8 deg. C., 1.52070 (Chuit); optically it is inactive also.

The product is usually sold in 10 or 20 per cent. alcoholic solution ready for use.

Jasmine.—This is one of the few cases in which the artificial oil is probably superior to that obtained from the natural flowers, possibly due to the extreme delicacy of the odour, and its consequent slight decomposition during preparation from the flowers. The chemical composition of the floral perfume has been very exhaustively studied, and the artificial article now on the market may be described as a triumph of synthetical chemistry. Among its constituents are benzyl acetate, linalyl acetate, benzyl alcohol, indol, methyl anthranilate, and a ketone jasmone.

Linalol, the alcohol forming the greater part of linaloe and bois de rose oils, and found also in lavender, neroli, petitgrain, bergamot, and many other oils. The article has the specific gravity at 15 deg. C., 0.870-0.876; optical rotation, -12 deg. to -14 deg.; refractive index at 20 deg. C., 1.463-1.464; and when estimated by acetylation, yields about 70 per cent. of alcohols.

Linalyl acetate, or artificial bergamot oil, is the ester formed when linalol is treated with acetic anhydride. It possesses a bergamot-like odour, but it is doubtful whether its value is commensurate with its greatly increased price over that of ordinary bergamot oil. It has the specific gravity at 15 deg. C., 0.912.

Musk (Artificial).—Several forms of this are to be obtained, practically all of which are nitro-derivatives of aromatic hydrocarbons. The original patent of Baur, obtained in 1889, covered the tri-nitro-derivative of tertiary butyl xylene. The melting point of the pure article usually lies between 108 deg. and 112 deg. C., and the solubility in 95 per cent. alcohol ranges from 1 in 120 to 1 in 200, though more soluble forms are also made.

An important adulterant, which should always be tested for, is acetanilide (antifebrin), which may be detected by the characteristic isocyanide odour produced when musk containing this substance is boiled with alcoholic potash, and a few drops of chloroform added. Acetanilide also increases the solubility in 95 per cent. alcohol.

Neroli Oil (Artificial).—Like jasmine oil, the chemistry of neroli oil is now very fully known, and it is therefore possible to prepare an artificial product which is a very good approximation to the natural oil, and many such are now on the market, which, on account of their comparative cheapness, commend themselves to the soap-perfumer. These consist chiefly of linalol, geraniol, linalyl acetate, methyl anthranilate, and citral.

Mirbane Oil or Nitrobenzene.—This is a cheap substitute for oil of bitter almonds, or benzaldehyde, and is a very coarse, irritating perfume, only suitable for use in the very cheapest soaps. It is prepared by the action of a mixture of nitric and sulphuric acids on benzene at a temperature not exceeding 40 deg. C. Its specific gravity is 1.205-1.206; refractive index at 20 deg. C., 1.550; and boiling point, 206 deg. C.

Niobe oil, or ethyl benzoate, the ester obtained from ethyl alcohol and benzoic acid, and having the specific gravity at 15 deg. C., 1.094-1.095; refractive index at 20 deg. C., 1.5167; boiling point, 196.5 deg.-198 deg. C.; soluble in 1.5 volumes of 70 per cent. alcohol.

Oeillet is a combination possessed of a sweet carnation-like odour and having as a basis, eugenol or isoeugenol. Its properties vary with the source of supply.

Rose Oil (Artificial).—Several good and fairly cheap artificial rose oils are now obtainable, consisting chiefly of citronellol, geraniol, linalol, phenyl ethyl alcohol, and citral. In some cases stearopten or other wax is added, to render the oil more similar in appearance to the natural article, but as these are inodorous, no advantage is gained in this way, and there is, further, the inconvenience in cold weather of having to first melt the oil before use.

Safrol, an ether which is the chief constituent of sassafras oil, and also found in considerable quantity in camphor oil. It is sold as an artificial sassafras oil, and is very much used in perfuming cheap toilet or household soaps. Its specific gravity at 15 deg. C. is 1.103-1.106; refractive index at 20 deg. C., 1.5373; and it dissolves in fifteen volumes of 80 per cent. alcohol.

Santalol, the alcohol or mixture of alcohols obtained from sandalwood oil. Its specific gravity at 15 deg. C. is 0.9795; optical rotation, -18 deg.; and refractive index at 20 deg. C., 1.507.

Terebene, a mixture of dipentene and other hydrocarbons prepared from turpentine oil by treatment with concentrated sulphuric acid, is used chiefly in medicated soaps. Its specific gravity at 15 deg. C. is 0.862-0.868; the oil is frequently slightly dextro- or laevo-rotatory; the refractive index at 20 deg. C., 1.470-1.478.

Terpineol, an alcohol also prepared from turpentine oil by the action of sulphuric acid, terpene hydrate being formed as an intermediate substance. It has a distinctly characteristic lilac odour, and on account of its cheapness is much used in soap perfumery, especially for a lilac or lily soap. Its specific gravity at 15 deg. C. is 0.936-0.940; refractive index at 20 deg. C., 1.4812-1.4835; and boiling point about 210 deg.-212 deg. C. It is optically inactive, and readily soluble in 1.5 volumes of 70 per cent. alcohol.

Vanillin, a white crystalline solid, melting at 80 deg.-82 deg. C. and prepared by the oxidation of isoeugenol. It has a strong characteristic odour, and occurs, associated with traces of benzoic acid and heliotropin, in the vanilla bean. It can only be used in small quantity in light-coloured soaps, as it quickly tends to darken the colour of the soap.



CHAPTER IX.

GLYCERINE MANUFACTURE AND PURIFICATION.

Treatment of Lyes—Evaporation to Crude Glycerine—Distillation—Distilled and Dynamite Glycerine—Chemically Pure Glycerine—Animal Charcoal for Decolorisation—Glycerine obtained by other Methods of Saponification—Yield of Glycerine from Fats and Oils.

As pointed out in Chapter II. the fatty acids, which, combined with soda or potash, form soap, occur in nature almost invariably in the form of glycerides, i.e., compounds of fatty acids with glycerol, and as the result of saponification of a fat or oil glycerine is set free.

In Chapter V. processes of soap-making are described in which (1) the glycerine is retained in the finished soap, and (2) the glycerine is contained in the lyes, in very dilute solution, contaminated with salt and other impurities. These lyes, though now constituting the chief source of profit in the manufacture of cheap soaps, were till early in last century simply run down the drains as waste liquor.

Much attention has been devoted to the purification and concentration of glycerine lyes; and elaborate plant of various forms has been devised for the purpose.