is a peculiar chemical compound of animal or vegetable oils and fats, with the alkalies. The use of soap does not date from a very early period; although mentioned in the Bible there is much reason to believe that alkali used in washing is meant, and not manufactured soap. It appears to have originated in Germany, and was introduced to the Romans about the beginning of the Christian era. At first its use seems to have been greatly misunderstood, for Pliny says, "Soap, too, is very useful for this purpose" (the dispersion of scrofulous sores), "an invention of the Gauls for giving a reddish tint to the hair. This substance is prepared from tallow and ashes, the best ashes for the purpose being those of the beech and yoke..." S O A P.
Soap.
There are two kinds of it, the hard soap and the liquid, both of these used by the people of Germany, the men in particular more than the women." It is more than probable that Pliny was mistaken in the motive of the Gauls for washing their heads with soap, and that the reason was cleanliness, which of course brightened the naturally light colour of their hair.
The aborigines of South America manufacture a kind of hard soap in a very peculiar manner; but whence they derived the art, or how long they have used it, is not known. They select a tree, which in the neighbourhood of Para is called Cherembu; this is cut down and burned to ashes, which are mixed with lime and Carapa oil, made from the large seeds of Carapa Guianensis, and, boiled, it is poured off from the ashes whilst liquid, and hardens on cooling. This soap is much used by the washerwomen in many parts of Brazil.
Many plants are found to have detergent properties similar to soap, and in the countries producing them are employed for washing. Thus, in the West Indies and tropical America, the berries of the soap-tree (Sapindus saponaria), are much used, and are found to be very far superior in cleansing power to common soap. Another South American tree, the Quillia saponaria, and perhaps other species of the same genus, yields a bark which has very powerful saponaceous qualities, and is not only used extensively in its native country, but has recently been introduced experimentally to this country, several importations having been received at Liverpool, for making a saponaceous solution for washing woollens. It is at least equal if not superior in strength to our best yellow soap. Where known, it is esteemed for washing the hair.
The natives of the Malayan Islands use the bark of the Gogo-tree (Entada pursetha) for the same purposes, and this bark is highly prized by the ladies of Manila for cleansing and brightening their beautiful tresses. Various other vegetable productions are used, but less extensively. The process of saponification is much varied, and considerable difference also exists in the oleaginous materials, consequently we find numerous kinds of soap in use for different purposes. The ordinary process consists in submitting oleaginous or fatty matters to the chemical action of alkaline lyes, and boiling the compound to get rid of a portion of the water used for the solution of the alkali. They may be arranged under the following heads—Hard, Soft, and Medicated Soaps, each of which comprises numerous varieties.
Common Hard Soap is of three kinds—yellow, white, and mottled. In making the yellow kind, the materials employed are tallow, grease, or kitchen and bone fat, palm-oil, resin, and the alkaline lye or solution of soda-ash, or crude carbonate of soda. The lye is prepared in the soda-vats, which are cast-iron cylinders about 6 feet wide by 4 or 5 feet in depth, and having perforated bottoms, below which is a large funnel for receiving the filtered lye. In the vat a layer of quick-lime is first placed, then successive layers of soda-ash and lime, through which water is allowed to percolate until it has dissolved about 2 per cent. of the alkali rendered caustic by the action of the quick-lime.
A ton of the fat melted in the boiler requires 200 gallons of the lye for the first process. They are gently boiled for four hours, and then allowed to cool; the partially formed soap subsides; and the lye is drawn off clear, and exhausted of its alkali. A second charge of fresh lye is then added, and the process repeated three times a day for about six days. Previous to the last boil, the resin is added, as it is too liable to be liquefied by the alkaline lyes if exposed to the action of the whole series; the quantity of resin must always be less than half the fats employed, and before using must be reduced to coarse powder. Palm-oil is generally one of the fatty ingredients when resin is employed, its pleasant violet odour and bright golden colour serving to disguise the resin. The great soaperies of Lancashire and Cheshire, which supply the vast export trade from Liverpool, produce most of the yellow soap made in England.
The soap is transferred from the boilers to the frames in a liquid state, and allowed to solidify by cooling. These frames are made of thick bars of wood, of the same width and length as an ordinary bar of soap; four of these are joined together, forming a square frame, and a number of these frames being placed one upon another, iron rods are passed through holes in the thickness of the wood, and being screwed up tight, form a sort of tank in which the liquid soap soon becomes solid. When this has taken place, the iron rods are withdrawn, and a thin piece of wire is inserted between the top frame and the one below it, and is made to cut through the soap in the line of the lower part of the frame. The top frame with its square of enclosed soap is then lifted off, and the process repeated until all the frames are separated. After a little exposure to the drying influence of the air, the soap is easily detached from the frames, and is then cut into bars and packed into boxes for sale.
Common White Soap is made in the same manner, with the exception of the palm-oil and resin, which are omitted, tallow being chiefly used, to which, in some sorts, cocoanut oil is frequently added.
Mottled Soap, which is almost peculiar to the London soaperies, is made of the same materials as the white soap, but previous to the last boil the mass is watered with a strong lye of crude soda, poured upon it by means of an ordinary gardener's watering-pot with a large rose. The mottling of the celebrated Castile soap is produced by a similar process, a solution of sulphate of iron being employed instead of the crude soda. In Southern Europe olive-oil is used instead of tallow, and forms a hard white soap.
The finer kinds of Hard Soap, or Toilet Soaps, are made of fine white tallow, suet, palm, olive, or almond oils, or a mixture of two or more of these, according to the quality required. The best Windsor soap is made with nine parts of fine tallow and one of olive-oil, the latter being preferred to suet, which is used for the inferior sort, in consequence of its slower saponification insuring a more perfect combination of the alkaline with the fat acids. The perfume used is a mixture of 6 lbs. of oil of caraway seed, 13 lb. of oil of lavender, and 13 lb. of oil of rosemary, to every 1000 lb. of the soap. The brown kind is coloured with burned sugar, or umber and Armenian bole; the latter colouring is used only for inferior sorts.
Honey Soap, now extensively used, is made by re-melting three other kinds, namely, palm-oil, olive-oil, and curd soaps, and scenting with the citronelle oil or essential oil of Androgon citratum, which gives it its peculiar honey scent. The other leading kinds of perfumed soaps are almond, rose, cinnamon, musk, and orange-flower soaps, all of which vary in their composition more or less, according to the taste of the manufacturer.
Soft Soap differs both in composition and in the process of its manufacture, from hard soap. Instead of soda being used for the alkaline, base potash is employed. The following is given by Dr Ure as the process:
"A portion of the oil being poured into the pan, and heated to nearly the boiling point of water, a certain quantity of the weaker lye is introduced, the fire being kept up so as to bring the mixture to a boiling state. Then some more oil and lye are added alternately, until the whole quantity of oil destined for the pan is introduced. The ebullition is kept up in the gentlest manner possible, and some strong lye is occasionally added, till the workman judges the saponification to be perfect. The boiling becomes progressively less tumultuous, the frothy mass subsides, the paste grows transparent, and it gradually..." thickens. The operation is considered to be finished when the paste ceases to affect the tongue with an acrid pungency, when all milkiness and opacity disappear, and when a little of the soap placed to cool upon a glass plate assumes the proper consistency."
The peculiar granular appearance of the soft soap used in this country, and which makes it so much resemble the pulp of ripe figs, is produced by the addition of small quantities of tallow, which are disseminated through the mass, and form the white specks. From its appearance when complete, this operation is technically called figging. The oils generally used are the fish, whale, and seal oils, but on the continent various seed-oils, especially those from hemp-seed, linseed, colza-seed, and poppy-seed. The continental soap-makers give the soft soap a green colour, which is sometimes produced by the addition of indigo.
Soft soap is much used in cleansing woollen fabrics, for which its superior solubility and great detergent power specially fit it. A very coarse kind is used by farriers under the name of black soap. There are a few varieties of soft soap used for toilet purposes, the principal of which is Naples soap, used chiefly for shaving. It is said to be made only from olive-oil and potash; but all imitations of it differ from the true Italian manufacture. It is much prized in consequence of its softening power upon the hair.
The Medicated Soaps have lately acquired some importance in pharmacy, particularly on the continent. The Castile soap, previously mentioned, is generally used as the base of these preparations. The most valuable of all medicated soaps is the Chlorinated, the Savon Antiphilitique of French pharmacy. It is made by working together one part of chloride of lime with eleven of Castile soap, using spirit of wine scented with oil of verbena to effect the incorporation. The mass is then fashioned into little flat cakes, and folded carefully in tinfoil or gutta-percha paper. It is powerfully detergent, and is very effective in removing stains, and is known to be of remarkable efficacy in preventing the effects of contagion, if the hands or clothes are washed with it. The other medicated soaps are antimonial, croton, guaiacum, iodine, mercurial, tar, turpentine, sulphuretted vitriol, &c., the formulæ for which are in the pharmacopoeias.
Arsenical soap is of considerable importance to the naturalist, being an effectual preservative of the skins of animals, particularly of birds, and those most liable to the attacks of moths. It is composed of carbonate of potash, twelve parts; of white arsenic, common white soap, and air-slaked lime, each four parts; and powdered camphor, one part, with enough of water to make it into a paste.
The rationale of the process of saponification was first explained by Chevreul, who showed that in the combination new substances capable of forming salts and possessing true acid properties are generated out of the elements of the fat, under the influence of the alkaline base. Common fat saponified consists of a mixture of stearic, margaric, and oleic acids, each combined with the base, and the peculiar neutral liquid substance called glycerine, which resembles colourless syrup, and is miscible with water. Glycerine is obtained from other sources than soap, and for commercial purposes is generally procured by refining the sweet liquor of the stearine-makers; it is now extensively used chiefly in pharmacy for external applications. When pure it is colourless, odourless, sweet to the taste, and of a syrupy consistency; it feels soft like oil, but has no greasiness, and it does not evaporate at ordinary temperatures; hence its value to the surgeons for keeping inflamed parts moist.
The importance of this branch of manufacture is very considerable, whether it be viewed with respect to its sanitary effects upon the human race, or in its bearing upon other important manufactures. In no country is it used to the same extent as in Great Britain; and, as a consequence, the skill of our chemists has been specially directed to its improved and economical production with so much success that, now the excise restrictions have left the soap-maker unfettered, we are enabled to produce all the really useful kinds, not only much cheaper, but also better, than the manufacturers of other countries; while in the ornamental varieties we beat our neighbours in cheapness, and are rapidly approaching them in elegance of production. The rapidity with which this branch of industry has developed in this country is truly marvellous. In the first year of the present century the consumption of soap was 52,947,037 lbs., but in 1850 it had reached the enormous quantity of 197,632,280 lbs. This increase during the half-century, viewed in relation to the increase in population, is quite as remarkable. In 1801 the quantity gave 4-84 lb. to each person, while that in 1850 gave 9-71 lb. It must not, however, be assumed from these facts that the personal use of soap had doubled, as a very great proportion of the increased consumption has been due to the extension of our manufactures in which soap is used, and to the origination of new branches of industry in which it is required.
The quantity of soap at present made in Great Britain cannot be ascertained with certainty, as the duty is now removed, and we have no excise returns; but the quantity is annually increasing to a great extent. Our exports alone amounted last year (1858) to 12,500 tons, the greatest portion of which was sent to our colonies. The States of South and Central America also received large quantities; the rest found its way to Austria, Italy, Sardinia, Turkey, Java, China, and Western Africa. (T.C.A.)