Long-chain fatty acid soaps

Long-chain fatty acids are insoluble in water, and their titration curves are concentration-dependent because of the formation of organized aggregates (acid soaps, soap micelles, fatty acid precipitates) which concentrate protons at the surface. At concentrations above the critical micellar concentration, solutions of long-chain fatty acid soaps manifest a diprotic curve when they are titrated from pH 10 to 4 (23). The first... 

Treatment of fats or oils with strong bases such as lye (NaOH) or potash (KOH) causes them to undergo hydrolysis (saponification) to form glycerol and the salt of a long-chain fatty acid (soap). 

A surfactant molecule is an amphiphile, which means it has a hydrophilic (water-soluble) moiety and a hydrophobic (water-insoluble) moiety separable by a mathematical surface. The hydrophobic tails of the most common surfactants are hydrocarbons. Fluorocarbon and perfluorocarbon tails are, however, not unusual. Because of the hydrophobic tail, a surfactant resists forming a molecular solution in water. The molecules will tend to migrate to any water-vapor interface available or, at sufficiently high concentration, the surfactant molecules will spontaneously aggregate into association colloids, i.e., into micelles or liquid crystals. Because of the hydrophilic head, a surfactant (with a hydrocarbon tail) will behave similarly when placed in oil or when put in solution with oil and water mixtures. Some common surfactants are sodium or potassium salts of long-chained fatty acids (soaps), sodium ethyl sulfates and sulfonates (detergents), alkyl polyethoxy alcohols, alkyl ammonium halides, and lecithins or phospholipids. 

Absorption bases have an alleged capacity to facilitate absorption by the skin, but the term also alludes to their ability to take up considerable amounts of water to form water-in-oil emulsions. Lipogels are gels prepared by dispersion of long-chain fatty acid soaps such as aluminium monostearate in a hydrocarbon base. Hydrogels prepared from Carbopols or... 

If the solubility of a surfactant is highly temperature-dependent, as is the case for many nonionic polyoxyethylene surfactants and long chain fatty acid soaps such as sodium stearate, it will be found that foaming ability will increase in the same direction as its solubility. Nonionic POE surfactants, for example, exhibit a decrease in foam production as the temperature is increased and the cloud point is approached (solubility decreases). Long-chain carboxylate salts, on the other hand, which may have limited solubility and poor foaming properties in water at room temperature, will be more soluble and will foam more as the temperature increases. 

Reaction with Fatty Acids and Esters. Alkanolamines and long-chain fatty acids react at room temperature to give neutral alkanolamine soaps, which are waxy, noncrystaUine materials with widespread commercial appHcations as emulsifiers. At elevated temperatures, 140 —160°C, A/-aIkanolamides are the main products, at a 1 1 reaction ratio (7,8). 

Stearic acid is the most common of the long-chain fatty acids. It is found in many foods, such as beef fat and cocoa butter. It is widely used as a lubricant in soaps, cosmetics, food packaging, deodorant sticks, and toothpastes. It is also a commonly used softener in rubber. 

The alkaline product from the wood ash was a crude solution of sodium and potassium carbonates called "lye". On boiling the vegetable oil with the lye, the soap (sodium and potassium salts of long chained fatty acids) separated from the lye due to the dispersive interactions between the of the fatty acid alkane chains and were thus, called "lyophobic". It follows that "lyophobic", from a physical chemical point of view, would be the same as "hydrophobic", and interactions between hydrophobic and lyophobic materials are dominantly dispersive. The other product of the soap making industry was glycerol which remained in the lye and was consequently, termed "lyophilic". Thus, glycerol mixes with water because of its many hydroxyl groups and is very polar and hence a "hydrophilic" or "lyophilic" substance. 

Detergents act as emulsifiers, breaking the oil into tiny droplets, each suspended in water. The disruption of the oil film allows the dirt particles to become solubilized (they peptize). Soap, the sodium or potassium salt of long-chain fatty acids, is a good detergent, although it often forms insoluble compounds with certain salts found in hard water, thus diminishing its effectiveness. 

Soaps are the detergents used since long. Soaps used for cleaning purpose are sodium or potassium salts of long chain fatty acids, e.g., stearic, oleic and palmitic acids. Soaps containing sodium salts are formed by heating fat (i.e., glyceryl ester of fatty acid) with aqueous sodium hydroxide solution. This reaction is known as saponification. 

Uses. Reacts with long-chain fatty acids to form ethanolamine soaps, which are used extensively as emulsifiers, thickeners, wetting agents, and detergents in cosmetic formulations also used as a dispersing agent in agricultural chemicals as a chemical intermediate as a corrosion inhibitor... 

A better method for studying the alkali metal cation-soap anion interaction on the surface, according to Weil (58), is to assume a similarity between surface behavior and solution behavior and to use the activity coefficient of the solute in the solution as the parameter to account for surface behavior. By plotting activity coefficients as a function of the molality for the salts of the alkali metals (7, 26), the resulting order of the curves of the weak acids (formates, acetates, hydroxides) is the reverse of that found for the strong acids (chlorides, bromides, nitrates, chlorates, sulfates). The activity curves of the acetate salts can be used as the counterparts for the long-chain fatty acid salts, while those for the chlorides can be the analogs of the alkyl sulfates. The scheme is speculative in that the fatty acid and alkyl sulfate salts micellize, and acetate and chloride do not. 

Colorimetry. Copper (Duncombe 1963 Koops and Klomp 1977) or cobalt (Novak 1965) soaps of long-chain fatty acids (>C12) are soluble in chloroform and can be determined quantitatively by colorimetric determination of the extracted metal. Shipe et al. (1980B) have recently modified the original copper soap method to make it simpler, more rapid, and adaptable to automatic equipment. 

Zinc soaps, which are complexes of long chain fatty acids, find similar applications in the curing and hardening of coatings to other transition metal soaps. A summary is available.123 The more important anions are 2-ethylhexanoate, naphthenate and stearate. Mixtures of zinc and calcium soaps are also effective stabilizers for poly(vinyl chloride).124 The complexes [Zn 0P(0)-(OBun)2 2] and [Zn SP(S)(OBun)2 2] both promote antiwear properties of lubricating oils.125... 

Soluble amphiphiles are also known as detergents, tensides, or surfactants. Perhaps the most descriptive of these words is the word surfactant, which is a contraction of the phrase surface active agent . The term soap is usually restricted to the alkali metal salts of long-chain fatty acids (Table 12.1). The term amphiphile indicates that one part of the molecule likes a certain solvent while the other part likes another solvent and the two solvents are immiscible. Usually one solvent is water and the water-loving part is called hydrophilic. The other part is hydrophobic. It does not like to be in water and prefers to be in an oily environment or air. The hydrophobic part usually consists of a long, straight alkyl chain (CH3(CH2) c i nc = 8-20). For special applications the hydrocarbons might be completely or partially fluo-rinated. 

Soaps have been used as detergents for many centuries. Soap normally consists of the sodium or potassium salts of various long-chain fatty acids and is manufactured by the saponification of glyceride oils and fats (e.g. tallow) with NaOH or KOH, giving glycerol as a by-product ... 

A soap is the sodium or potassium salt of a long-chain fatty acid. The fatty acid usually contains 12 to 18 carbon atoms. Solid soaps usually consist of sodium salts of fatty acids, whereas liquid soaps consist of the potassium salts of fatty acids. 

Long-chain fatty acids are relatively insoluble in polar media, but they still form salts, some of which act as detergents (soaps) and thus associate with hydrophobic lipids in the lipoproteins. 

Soaps—Salts of long-chain fatty acids... 

Soap (Sections 3.6, 22.12B) The carboxylate salts of long-chain fatty acids prepared by the basic hydrolysis or saponification of a triacylglycerol. 

Commonly used repeUents for leather are sUicones, chrome complexes of long chain fatty acids, and fluorochemicals. Fluorochemical repeUents also provide repeUency to oUs and greases so that the treated leather resists staining. A water repeUent may also be a hydrophobic chemical insolubUized in the leather. A simple water-repeUent treatment consists of forming an aluminum soap in leather by the two-step process of applying a soap, and then an aluminum salt. 

Saponification refers to alkaline hydrolysis of fats and oils to give glycerol and the alkali metal salt of a long chain fatty acid (a soap). In this experiment saponification of olive oil is accomplished in a few minutes by use of a solvent permitting operation at 160°C. Of the five acids found in olive oil, listed in Table 1, three are unsaturated and two are saturated. Oleic acid and linoleic acid are considerably lower melting and more soluble in organic solvents than the saturated components, and when a solution of the... 

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