Soap

SOAP, in chemical terms, is a mixture of soluble salts of fatty acids (both saturated and unsaturated series) with at least 8 carbon atoms in the molecule. In the homologous series of fatty acid salts, sodium caprylate C₇H₁₅COONa is the first to exhibit soap properties, forming foam with water and creating a gelatinous substance under the influence of common salt. The first reliable information about soap is provided by Pliny the Elder (1st century CE). During excavations in Pompeii, a soap-making workshop was discovered. At that time, soap was prepared from ash and tallow in the form of a mechanical mixture and was used for skin and hair. The French chemist Chev-reul (1823) provided the scientific basis for the soap-making process. The subsequent success of soap making was greatly facilitated by Leblanc's discovery in 1791 of a method for preparing soda from common salt. In Russia, soap making appeared in the 17th century, first in Novgorod, where this art was introduced from the Hanseatic cities with which the Novgorodians maintained relations. The development of soap making proceeded very slowly. Washing with soap was long considered a sin. The annual per capita consumption of soap in Russia before the war was 1.2 kg, while in other European countries the figure reached 8 kg, and in America up to 12 kg. At present, the pre-war level has not yet been reached. Soap dissolves easily in hot water, more slowly in cold water, forming cloudy solutions due to partial decomposition (hydrolysis). With alcohol, soap gives clear solutions; at high concentrations, solid soaps' alcoholic and glycerin solutions solidify in the cold. In ether, benzene, and other solvents, soap is almost insoluble. Soap is prepared from animal and vegetable fats. In the former, solid fatty acids predominate, in the latter, predominantly liquid ones. The main fats in Soviet soap making are natural and hydrogenated (processed into solid fat) vegetable oils. About 75% of the soap produced in the USSR is made from sunflower oil, 10% from cottonseed oil, and the remaining 15% from linseed, hemp, coconut, and animal fats. The quality of soap, its cleansing ability, and other chemical and physical properties depend on the nature of the fatty acids and bases that form it. The cleansing action of soap represents a complex physicochemical process. Existing theories explain this process insufficiently comprehensively. Chev-reul and Berzelius (1838) believe that under the influence of water, soap breaks down into free alkali and acid salt of fatty acids. The free alkali saponifies and dissolves the fatty dirt on the body or fabric, while the water-insoluble acid salt is mechanically removed along with the unsaponified part of the dirt. According to Knapp, soap solutions, by reducing the surface tension between water and the object being washed, wet the surface faster than water. The dirt particles are enveloped by soap, which facilitates cleaning. Penetrating between the wetted surface and dirt particles, soap separates the dirt from the object, and water washes it away. According to Rotondi's theory, when acted upon by water, neutral soap breaks down into basic and acid fatty acid salts. No free alkali is formed in this process. The role of free alkali is played by the basic fatty acid salt, which is easily soluble in water. According to Kraft, the cleansing ability of soap depends on the nature of the fatty acids contained in it. More recently, a new theory has been proposed, developed by Spring and Goldschmidt and based on the colloid-chemical nature of soap; an aqueous solution of soap has the ability to convert finely divided substances into a colloidal solution; the soap solution has a stronger attraction than the fabric, and therefore dirt particles pass into the soap solution. This phenomenon is called adsorption, or agglutination. Aqueous solutions of soap remove dirt better than alcoholic ones. The optimal concentration of soap solutions for washing purposes depends on the type of soap and the quality of water, as hard water requires more soap than soft water. The best results are given by 0.25%-0.5% solutions; a 2% solution has a lower cleansing effect than a solution containing 0.125%. During washing, dirt absorbs a significant amount of soap, which is evidenced by the rapid disappearance of foam when washing dirty items. Soap has hygienic significance. A soap solution is a weak disinfectant. Increasing t⁰ enhances the disinfecting effect. Hard water and other soap precipitants reduce the disinfecting effect. Liquid soap, containing much water and glycerin, has less disinfecting ability than solid soap. Rosenhagen asserts that a solution of pure neutral soap has no effect on bacterial spores. The sanitary significance of soap is mainly related to its mechanically cleansing properties. Soap moistens the skin. Friction during washing stimulates the excretory glands and promotes the exfoliation of dead epidermis. By removing the dirty covering of the skin, soap restores its normal elasticity and firmness and enhances the tactile properties of the skin. Washing with soap prepares the skin before surgery and facilitates deeper penetration of the disinfectants subsequently applied. Soap is divided by external appearance into hard soap (usually soda soap) and soft soap (potassium soap). By method of boiling, it is divided into kernel soap, semi-kernel soap (Eschwege soap), and glue soap. The first two varieties are always prepared with heating (hot-boiled soap); glue soap, in addition to the hot method, can also be obtained cold, especially when made from coconut fat (cold-boiled soap). Kernel soap is obtained by salting, i.e., treating the soap solution obtained after boiling with salt. Soap does not dissolve in salt water and is completely precipitated from the solution. Kernel soap is free from glycerin obtained during saponification of fat, excess alkali, and most of the water introduced into the saponification reaction. Kernel soap is considered the best, so-called true soap, and is most economical. Semi-kernel soap (Eschwege soap, marble soap) is obtained by boiling a mixture of palm or coconut oils and other fatty substances. Semi-kernel soap contains more water than kernel soap. Glue soap, both hot and cold boiled, retains all the water and glycerin formed during the saponification reaction, and is therefore even less advantageous for the consumer. The disadvantage of cold-boiled soap is the incomplete combination of fatty substances with alkali and, as a result, rapid rancidity of the soap and the presence of free alkali, which is harmful to the skin. Inexpensive toilet soaps and so-called transparent glycerin soaps are usually made by the cold method. In relation to water, soap is divided into water-soluble (soda soap, potassium soap) and water-insoluble (fatty acid salts of other metals, for example, plasters). For medical purposes, lead soap is more widely used than others, which serves as the basis for lead plasters, and copper soap, which is part of preparations used in the treatment of ulcerative processes of a specific nature - tuberculous, syphilitic, soft chancre, fungal, and non-specific ulcerative processes, in cases of persistent, stubborn, and limited lichenoid dermatoses, in difficult-to-heal varicose ulcers and bedsores. For the purpose of reducing cost and imparting certain mechanical and chemical properties to soap, 1) rosin (harpius) is added, in an amount of up to ¹/₃ by weight of fat before saponification. Rosin increases the solubility of soap and promotes foaming. 2) Soap-naphtha - neutralized alkali waste from petroleum distillation, containing naphthenic acids with a molecular weight suitable for soap. A valuable property of soap-naphtha is its low degree of hydrolysis and foaming ability, good insecticidal action; the disadvantage (sometimes with poor purification) is a persistent kerosene smell. Fillers are added to soap - kaolin (porcelain clay), colloidal and fuller's earth clay, sodium silicate and sulfate, marble clay, talc, starch. Without enhancing the cleansing action of soap, fillers, as pure weight additives, only adulterate the soap. Saponin preparations, powders of saponin-containing plants (soap root), and soapstone (kil) are also fillers, but not devoid of cleansing action. According to the STO standard in the USSR, the following varieties of household soap are permitted for sale: kernel, Eschwege, and glue soaps. Technical specifications: A. Physical properties: 1) Soap must be hard and dry, there should be no films or excretions on the surface of the soap. 2) Soap should not have a bad smell. 3) The foaming of soap should be clearly manifested at t° of 25°. 4) On Eschwege soap, the marble should have a clearly defined structure. B.

Chemical properties: 1) Fatty acids should be in S. not less than 60% in kernel and 47% in Eshwege and glue. 2) Harpious (resinous) acids should not be more than 15% of the total weight of fatty acids. 3) Unsap and unsaponifiable substances in relation to the total weight of fatty acids should be in total not more than 1% in kernel and 1% in Eshwege. 4) Free caustic alkali should not be more than 0.2% of the weight of S. 5) Water-insoluble residue should not be more than 0.8% of the weight of S. - Standards for soft S.: 1) consistency is ointment-like; 2) color is transparent; 3) odor - absence of unpleasant odor; 4) stability during storage - no separation of solid or liquid substances from the main mass should be observed; 5) content of fatty acids and everything that is attributed to them in analysis - from 38% to 40% by weight of S.; 6) content of unsaponifiable substances not more than 1% by weight of S.; 7) content of free alkali from 0.5% to 1% by weight of S.; 8) content of fillers from 2% to 8% by weight of S. For medical soft ("green") soap F VII imposes higher requirements, especially regarding the absence of fillers and the limit of free alkali. - Toilet S. are made from a base consisting of kernel, semi-kernel and glue soap. The soap base after a series of mechanical processes is perfumed and often colored. Toilet S. must be completely neutral, contain unsaponified fat, must lather well and give the skin a pleasant odor. The added dye must be completely soluble in water. - Medical S. contain an admixture of medicinal or disinfecting substances. Medical S. must be absolutely neutral (except for special alkaline S.), made from the best materials. - Over-fatted soaps represent neutral S. with an admixture of lanolin. Lanolin, added in the amount of 5-10% of the weight of the fat, is strongly absorbed by animal skin and this property, in connection with resistance to rancidity, forms the basis of its use as an over-fattening agent. The disadvantage is the clogging of the excretory ducts of the skin glands, which complicates the action of the medicinal principle. Previously used for obtaining over-fatted S. almond and Provence oils have now been abandoned by industry due to rapid rancidity. The most common are tar S. with a content of from 3% to 10% tar in solid or liquid S. For colorless tar S., decolorized tar (anthrasol or pytral), largely freed from pyridine bases, is used. Sulfur S. occupies the same place with a content of from 2% to 10% sulfur. The alkali of the soap base forms with sulfur sulfurous alkali, causing skin irritation. The combination of sulfur and tar gives sulfur-tar S. Of value in therapeutic terms is ichthyol S. with a content of from 8% to 10% ichthyol. Ichthyol soap has keratoplastic, disinfecting and analgesic action. Thymol S. (10%) has the same action and is odorless. Sublimate S. Sublimate in S. loses its disinfecting properties, giving through exchange decomposition a fatty acid salt of mercury, and with prolonged storage is reduced to metallic mercury; S. in this case takes on a dirty gray color. More stable are afridol and providol S. (German patent), containing more active than the fatty acid salt of mercury, alkaline salts of mercury oxide-carboxylic acids. Carbolic S. has the same disadvantage as sublimate S. Phenol, added to S. in the amount of from 2% to 4%, partly volatilizes and partly turns into sodium phenolate, which does not have disinfecting properties. This transition occurs even in a neutral soap base. More stable are cresol S. (see Lysol), as well as lysol (see). Other S. with various medicinal ingredients have limited application. These include salicylic S. (during storage the acid turns into salt), perborate S. (in the presence of moisture they give off oxygen), gasoline S. in the form of a cream for removing fatty and resinous stains, bile S. (stain remover), mercury S. containing up to 50% metallic mercury, cod liver oil S. (used as children's S.), turpentine S. (40%) in the form of an ointment as a remedy for rheumatism, S. with ammonium sulfate and ammonium chloride (5%), S. with tincture of arnica (10%), chloroform S. (25%), iodoform S. (15%), iodol S. (10%), creosote S. (10%), pumice S. (20%), S. with potassium iodide (5-10%), S. with salol (5%), styrax S. (20%), S. with zinc oxide (10%), borax S. (10%), camphor S. (5%), naphthalene S. (2%), tannin S. (7%), alum S. (5%), aristol S. (2%), chrysarobin S. (5%), creolin S. (10%) and others, used in accordance with the influence of the active principle added to S. Due to the brief contact with the skin under the conditions of S. use and usually the small amount of medicinal and disinfecting principle, insoluble in many cases in water, and its inertia or incompatibility with the soap base, medical S. hardly exceed the value of ordinary S. Only in cases where the soap mass containing the medicine remains in contact with the skin for a long time (as mercury soap is sometimes used), medical S. can justify their value as a medicinal form. - Soap powders represent a mixture of S., usually prepared from low-grade fat and calcined soda. The content of fatty acids varies between 5% and 30%. Due to easy solubility, good lather and convenience of use, soap powders have found wide application. Therapeutic use of S. S. is taken internally 0.1-0.3 and up to 1.0, 2-4 times a day as a stimulant of secretion of the stomach, pancreas, intestines and bile. In large doses it causes nausea, vomiting and dyspepsia. In case of poisoning with acids, S. is taken as an antidote. Externally S. is used in the forms of plasters, ointments, liniments, tooth powder, tooth paste. In enemas and suppositories 1.0-2.0-4.0 as a laxative. Recent experiments indicate that the use of S. internally and in enemas should be avoided, as it causes a number of pathological changes (ulcers, bleeding). Pharmacopeial preparations. In F VII a small number of soap preparations is included. - Medical S. (soda, in powder), prepared from a mixture of lard and olive oil by saponification with caustic soda followed by salting; powder is white, almost odorless; dissolves in water and alcohol, forming a transparent or almost transparent solution. It should not have the smell of rancid fat and should not leave greasy spots on paper (unsaponified fat). In addition to external use, the powder is suitable for internal administration. Green S., obtained by saponification of hemp or sunflower oil with a solution of caustic potash. - Soap spirit of Hebra (F. Heb-ra)-water-alcohol solution of green S., scented with lavender oil; a mild skin irritant for washing in psoriasis of hairy parts of the body. - Lead plaster simple - lead S., prepared on a mixture of lard and wood oil. - Lead plaster complex - an alloy of simple lead plaster, rosin and turpentine. - Liniments - see Ointments. The quality of soap is directly dependent on the amount of pure alkaline fatty acid salts it contains, so-called pure true soaps. The analysis is divided into the following operations: 1) determination of the total amount of fat (fatty acids), 2) determination of neutral fat, 3) determination of the total amount of alkali: a) determination of bound alkali with fatty acids, b) determination of unbound alkali present in the form of carbonates, silicates, etc., c) determination of free alkali, 4) determination of water, 5) determination of impurities: a) inorganic and b) organic (especially resins). M. Tsypkin. In medical and judicial practice, cases are observed of introducing solutions of soap into the body with various pathological consequences. Thus, cases of intravaginal and intrauterine use of S. for the purpose of expulsion of the fetus are described, with severe changes in the form of necrosis of the mucous membrane, muscles, as well as hemorrhages and thrombi in the ovaries, tubes (N. Runge). Similar changes are also described when S. is taken internally (Langer, Johannsen). It is very probable, however, that in all such cases, along with the action of S., there is also the action of free alkali. When S. was experimentally introduced into the rectum of a rabbit, it turned out that already 12-24 hours after the introduction of a 1-2% solution of gray (green) S., significant changes (ulcers, hemorrhages) occurred in the large intestine, especially at the tops of the folds. Since the same changes are also observed in experiments with kernel S. containing little free alkali, the above effect should also be attributed to the action of the soap itself. In similar experiments on humans (N. Runge, H.

Hartmann) in ¹/₃ of cases also traces of pathological changes were found in the form of a positive reaction to blood in the contents of the rectum 1-3 days after the enema with M.; on the basis of these experiments, the mentioned authors recommend avoiding the use of M. FOR ENEMAS. I. Davydovsky. Soap production. The basis of the chemical process used in obtaining soap is the so-called saponification of fats, which consists in the fact that caustic soda or potassium combines with the fatty acids of the fat, and the glycerin contained in it is released in a free state. It is significantly more economical to obtain M. directly from fatty acids, for which preliminary splitting of the fat is required, i.e., the separation of neutral fat into fatty acids and glycerin. Of the various methods of splitting, the most common in soap making is the autoclave method, i.e., the treatment of fat with water at heating and increased pressure in the presence of lime as a catalyst in special hermetically sealed boilers (autoclaves). The most important fatty acids used in soap making processes are stearic, palmitic, and oleic. Unlike the first two, oleic acid is liquid at ordinary t° and constitutes the main component of vegetable oils, which are the cheapest and most readily available raw material for soap making. But since M. obtained from the treatment of oleic acid is too soft and easily dissolves, it became necessary to convert the unsaturated oleic acid into the saturated solid acid-stearic acid, which is achieved by adding hydrogen to the first in the presence of a catalyst (nickel). This process is called hydrogenation (see), or hydrogenization, and is carried out in special plants or in a separate auxiliary department in soap factories. The solid fats obtained after hydrogenation are called in our country salomas. The soap making process consists of the following. Large boiling vats are loaded with fats or fatty acids, then caustic alkali or calcined soda, rosin and other substances are added to them. The entire mixture is thoroughly stirred and steam is passed through coils in the vats, with which the mass is boiled for 18-20 hours. After the boiling is finished, the finished M. is poured into special molds, where it solidifies, after which it is cut into blocks, which then go to the stamping press, and from there to packaging. This production process, common in the manufacture of most varieties of M. (core, marble, glue, etc.), in the production of toilet soap consists of a significantly larger number of operations and requires more complex equipment. After the usual boiling and cooling, toilet soap is cut into thin shavings on cutting machines, which are then partially dried in special dryers, after which the soap shavings are mixed with coloring and fragrant substances and passed through roller (or otherwise called piliro) machines, from which comes an evenly colored strip of M., which is then on special molding machines (sausage) converted into dense, compact pieces of the appropriate shape. On presses of various systems (screw, impact, manual, etc.), pieces of soap are stamped, rubbed with flannel (for shine), wrapped in paper and sent to packaging. In the most rationally organized soap factories, in addition to the soap making workshop itself, there are a number of important auxiliary departments (gas generator, hydrogenation, etc.), which together form a combined enterprise consisting of differently equipped parts, each of which is of particular interest from the point of view of professional hygiene. The main installations of gas stations producing water gas and hydrogen are gas generators (see), with the operation of which a number of professional hazards are associated (high t°-22-38°, radiant energy, carbon monoxide, hydrogen sulfide, sulfur dioxide, coal dust), which can be largely eliminated when gas stations are equipped with technically perfect installations (Morgan system gas generators). In other departments of gas stations (hydrogen, gas purification, gas ventilation), the harmful gases mentioned are also released, and the t° in them, especially in the last two departments, is often very low in winter. In the hydrogenation department, two main production processes take place - preparation of the catalyst and the actual hydrogenation process (see Hydrogenation). When treating nickel with concentrated sulfuric acid (for its regeneration), various gases (CO, H₂S, H₂) enter the air of the premises, in addition, there is a danger of burns from splashing acid during this work. When grinding nickel carbonate and infusorial earth in apparatus, a large amount of very fine dust (NiCO₃ and SiO₂) is formed, which due to its high dispersion has the ability, when inhaled, to penetrate into the deep parts of the lungs. Similar conditions are created in the retort department, where workers load retorts with nickel carbonate and unload reduced nickel from them. The hydrogenation process itself, taking place in autoclaves, causes an increase in air temperature at the workplace, reaching 33-40° in winter months and 48° near the autoclaves and 44° at the compressors in summer. In addition, there is charring of oil that gets on the hot surface of autoclaves, which can lead to the formation of acrolein vapors (see), capable of causing acute professional poisoning under certain conditions. Among other toxic gases, carbon monoxide should be noted, found near autoclaves in an amount (0.11 mg/l) exceeding the maximum allowable concentration for this gas (0.01-0.02 mg/l) in the air of work premises. The most commonly used caustic alkalis in soap making pose a danger to workers in terms of burns and eye injuries. Various skin diseases in the form of eczema have also been repeatedly noted in workers handling solutions of caustic soda; in some cases, these ailments forced workers even to change their profession. When switching to work with calcined soda, these phenomena usually disappeared. The replacement of caustic soda with soda should be considered in this respect a very favorable factor, capable of significantly detoxifying and securing processes involving contact with caustic alkalis, especially when loading boiling vats. Due to the circulation of hot steam in the coils of the vats for many hours, as well as the constant evaporation of liquid from the surface of the vats, the t° and humidity in soap making workshops are quite high (t° up to 27-30° and humidity up to 82%). The boiling process itself is accompanied by the release of various vapors into the air of the premises, which are harmful to the body. The waste products of production, which usually accumulate in large quantities in the premises (on walls, floors), are also a constant source of air pollution. These substances undergo decomposition and their foul-smelling decomposition products poison the air. In addition, when making medical M., various toxic chemical substances (nitrobenzene, phenol, sublimate) are used, which in themselves can be a source of harmful gases and vapors capable of causing specific professional poisonings. In the manufacture of toilet soap, the above-mentioned production processes, especially the moments associated with the preparation of soap powder and the formation of dust, often serve as the cause of acute diseases of the mucous membranes of the eyes, nose, as well as the upper respiratory tract. Mechanization of all these works using sufficiently airtight equipment can eliminate these hazards. It should also be noted that due to constant contamination of the floors in soap making workshops, relatively frequent falls of persons working there are observed, often leading to bruises. When vats are located low above floor level or when work is done mixing the mass on unguarded platforms or boards, cases of workers falling into vats have been observed, mostly with fatal outcomes. Among the main health improvement measures to be carried out in soap factories, the first place should be given to the need for isolated storage of raw decaying materials in specially equipped warehouses outside the work premises; the installation of suction devices above boiling vats for complete removal of vapors released from them; mechanization of all processes involving the use of caustic substances; the installation of strong platforms with railings around the vats; the installation of mechanical devices for mixing the soap mass in boiling tanks. Legislation on labor protection in soap making. In France, the employment of women and adolescents under 18 years of age is prohibited in workshops where fats are extracted from solutions, as well as where carbon disulfide is used. In Holland, mandatory registration of cases of skin and lung diseases and ulcerative processes on the mucous membranes of the nose and oral cavity found in persons in contact with soap powder has been introduced.

In the USSR, safety regulations for work in soap production are provided for by the mandatory decree of the NKTS USSR of 21/XI 1924, № 477/486. In Ukraine, a mandatory decree on the protection of labor of workers in tallow-rendering, soap-making, and glue-making plants was issued on December 19, 1922.