Ferric hydrate, iron soaps and all insoluble impurities are precipitated.
Soaps give an alkaline reaction and have a decided acrid taste; in a pure condition - a state never reached in practice - they have neither smell nor colour.
Almost without exception potash soaps, even if made from the solid fatty acids, are " soft," and soda soaps, although made with fluid olein, are " hard "; but there are considerable variations according to the prevailing fatty acid in the compound.
Almost all soda soaps are precipitated from their watery solutions by the addition of a sufficiency of common salt.
Ammonia soaps have also been made, but with little commercial success; in 1906 H.
Resin soaps are compounds of soda or potash with the complex acids (chiefly abietic) of which coniferous resins consist.
Numerous varieties of soaps are made; the purposes to which they are applied are varied; the materials employed embrace a considerable range of oils, fats and other bodies; and the processes adopted undergo many modifications.
As regards processes of manufacture soaps may be made by the direct combination of fatty acids, separated from oils, with alkaline solutions.
All other soaps result from the combination' of fatty oils and fat with potash or soda solutions under conditions which favour saponification.
In such condition ordinary soft soaps and certain kinds of hard soap are brought to the market.
In curd soaps, however, which form the basis of most household soap, the uncombined alkali and the glycerin are separated by " salting out, " and the soap in this condition contains about 30% of water.
Ox and sheep tallow, with the addition of resin, are the primary materials for making the hard yellow or primrose soaps; these tallows are often adulterated.
The cheaper mottled and brown soaps have for their basis bone fat, obtained by treating bones with superheated steam or other methods.
Of the vegetable oils, in addition to cotton-seed and coco-nut, olive oil is the basis of soaps for calico printers and silk dyers; castor oil yields transparent soaps (under suitable treatment), whilst crude palm oil, with bone fat, is employed for making brown soap, and after bleaching it yields ordinary pale or mottled.
The cold process, which is Drily applicable to the manufacture of soaps from readily saponifiable oils, such as those of the coco-nut oil group and also from castor oil, is but little used.
By blending the coco-nut oil with other less saponifiable substances such as tallow, lard, cotton-seed oil, &c., and effecting the mixing and saponification at a slightly higher temperature, soaps are obtained which resemble milled toilet soaps.
Soaps made by this process contain the glycerin originally present in the oil, but, in view of their liability to contain free alkali and unsaponified oil, the process has been largely given up.
The process of manufacturing soaps by boiling fatty acids with caustic alkalis or sodium carbonate came into practice with the development of the manufacture of candles by saponifying fats, for it provided a means whereby the oleic acid, which is valueless for candle making, could be worked up. The combination is effected in open vats heated by a steam coil and provided with a stirring appliance; if soda ash be used it is necessary to guard against boiling over.
But in all countries a mixture of several oils enters into the composition of curd soaps and the proportions used have no fixity.
In this way curd, mottled or marbled soap is formed, and such mottled appearance was formerly highly valued as an indication of freedom from excess of water or other adulteration, because in fitted soaps the impurities are either washed out or fall to the bottom of the mass in cooling.
Now, however, the mottled soaps, blue and grey, are produced by working colouring matter, ultramarine for blue, and manganese dioxide for grey, into the soap in the frame, and mottling is very far from being a certificate of excellence of quality.
The frames into which hard soaps are ladled for cooling and solidification consist of rectangular boxes made of iron plates and bound and clamped together in a way that allows the sides to be removed when required; wooden frames are used in the case of mottled soaps.
Marine Soap. - These soaps are so named because they are not insoluble in a strong solution of salt; hence they form a lather and can be used for washing with sea-water.
Being thus soluble in salt water it cannot, of course, be salted out like common soaps; but if a very concentrated salt solution is used precipitation is effected, and a curd soap is separated so hard and refractory as to be practically useless.
Its property of absorbing large proportions of water, up to 80%, and yet present the appearance of a hard solid body, makes the material a basis for the hydrated soaps, smooth and marbled, in which water, sulphate of soda, and other alkaline solutions, soluble silicates, fuller's earth, starch, &c. play an important and bulky part.
Coconut soap also forms a principal ingredient in compound soaps meant to imitate curd and yellow soaps.
Two principal methods of preparing such compound soaps are employed.
The silicate in the form of a concentrated solution is crutched or stirred into the soap in a mechanical mixing machine after the completion of the saponification, and it appears to enter into a distinct chemical combination with the soap. While silicate soaps bear heavy watering, the soluble silicate itself is a powerful detergent, and it possesses certain advantages when used with hard waters.
Soft Soap. - Soft soaps are made with potash lyes, although in practice a small quantity of soda is also used to give the soap some consistence.
Toilet Soaps, &c. - Soaps used in personal ablution in no way differ from the soaps previously alluded to, and may consist of any of the varieties.
Transparent soaps are prepared by dissolving ordinary soap in strong alcohol and distilling off the greater portion of the alcohol till the residue comes to the condition of a thick transparent jelly.
Toilet soaps of common quality are perfumed by simple melting and stirring into the mass some cheap odorous body that is not affected by alkalis under the influence of heat.
The finer soaps are perfumed by the cold method; the soap is shaved down to thin slices, and the essential oil kneaded into and mixed with it by special machinery, after which it is formed into cakes by pressure in suitable moulds.
The greater quantity of high-class toilet soaps are now made by a milling process.
Soaps are also prepared in which large proportions of fine sharp sand, or of powdered pumice, are incorporated, and these substances, by their abrading action, powerfully assist the detergent influence of the soap on hands much begrimed by manufacturing operations.'
Medicated soaps, first investigated scientifically by Unna of Hamburg in 1886, contain certain substances which exercise a specific influence on the skin.
A few medicated soaps are prepared for internal use, among which are croton soap and jalap soap, both gentler cathartics than the uncompounded medicinal principles.
Medicated soaps for external use are only employed in cases of skin ailments, as prophylactic washes and as disinfectant soaps.
The so-called " floating soaps " are soaps made lighter than water either by inserting cork or a metallic plate so as to form an air space within the tablet.
Shaving soaps, which must obviously be free from alkali or any substance which irritates the skin, are characterized by readily forming a permanent lather.
This property is usually obtained by mixing soft and hard soaps, or, more rarely, by adding gum tragacanth to a hard soap. In the textile trades the wool scourer employs a neutral olive-oil soap, or, on account of its cheapness, a neutral curd or curd mottled brand; the cotton cleanser, on the other hand, uses an alkaline soap, but for cleaning printed cottons a neutral olive-oil curd soap is used, for, in this case, free alkali and resin are objectionable; olive-oil soap, free from caustic alkali, but often with sodium carbonate, is also used in cleansing silk fibres, although hard soaps free from resin are frequently employed for their cheapness.
Soaps of smaller moment are the pearl ash soaps used for removing tarry stains; ox-gall soaps for cleaning carpets; magnesia, rouge and chalk soaps for cleaning plate, &c.
The water in a soap is rarely directly determined; when it is, the soap, in the form of shavings, is heated to 105° C. until the weight is constant, the loss giving the amount of ' " Soap powders " and " soap extracts " are powdered mixtures of soaps, soda ash or ordinary sodium carbonate.
With genuine soaps, however, it suffices to calculate the fatty acids as anhydrides and add to this the amount of alkalis, and estimate the water by difference.
Medicated soaps are made by adding the drug to either hard soap or curd soap in the desired proportions.
Lamborn, Modern Soaps, Candles and Glycerin (1906); W.
Among other important articles of domestic industry are tobacco and cigars (manufactured mainly in bond, within the free harbour precincts), hydraulic machinery, electro-technical machinery, chemical products (including artificial manures), oils, soaps, india-rubber, ivory and celluloid articles and the manufacture of leather.
Among other manufactures are butter and cheese, canned fruits and vegetables, glass and earthenware, printing and wrapping paper, furniture, matches, hats, clothing, pharmaceutical products, soaps and - p erfumery, ice, artificial drinks, cigars and cigarettes, fireworks anc candles.
The soluble soaps which are probably conveyed by the blood will be quickly taken up by such cells, synthetized into neutral fats, and stored in a non-diffusible form till required.
Some investigators hold that the soaps may become combined with albumin, and that on becoming incorporated with the cytoplasm they can no longer be distinguished as fat.