Fatty acid salts, solubility

Emulsifiers. Removing the remover is just as important as removing the finish. For water rinse removers, a detergent that is compatible with the remover formula must be selected. Many organic solvents used in removers are not water soluble, so emulsifiers are often added (see Emulsions). Anionic types such as alkyl aryl sulfonates or tolyl fatty acid salts are used. In other appHcations, nonionic surfactants are preferred and hydrophilic—lipophilic balance is an important consideration. 

Salts of Organic Acids. Calcium salts of organic acids may be prepared by reaction of the carbonate hydroxide and the organic acid (9). Calcium lactate [814-80-2] is an iatermediate ia the purification of lactic acid from fermentation of molasses. Calcium soaps, soaps of fatty acids, ate soluble ia hydrocarbons, and are useful as waterproofing agents and constituents of greases (9). 

Ether carboxylates are used not only in powdered detergents but in liquid laundry detergents for their hard water stability, lime soap dispersibility, and electrolyte stability they improve the suspension stability and rheology of the electrolyte builder [130,131]. Formulations based particularly on lauryl ether carboxylate + 4.5 EO combined with fatty acid salt and other anionic surfactants are described [132], sometimes in combination with quaternary compounds as softeners [133,163]. Ether carboxylates show improved cleaning properties as suds-controlling agents in formulations with ethoxylated alkylphenol or fatty alcohol, alkyl phosphate esters or alkoxylate phosphate esters, and water-soluble builders [134]. 

Durand, R. (1948) Investigations on hydrotropy. The solubility of benzene, hexane and cyclohexane in aqueous solutions of fatty acid salts. Compt. Rend. 226, 409 -10. 

In milk with a normal pH of 6.7, most of the acids are in the salt form and have much less flavor than if they were completely in the acid form (Kuzdzal-Savoie, 1980). In fact, acidification of milk greatly enhances the sensitivity of organoleptic detection of lipolysis in milk (Tuckey and Stad-houders, 1967). The detection of rancidity is reduced by the association of the FFAs with certain proteins in milk (Parks and Allen, 1979 Keenan et al., 1982) and by heating of milk (Kintner and Day, 1965). The phase in which the fatty acids are soluble also influences their flavor threshold, since the short-chain acids have much lower thresholds in fat than in water, while the opposite applies to the long-chain acids (Patton, 1964). For example, butyric acid (C o) has a flavor threshold of 7 mg/kg in water, but only of 0.6 mg/kg in oil (Delahunty and Piggott, 1995). 

Ambrette Seed Oil occurs as a clear yellow to amber liquid with the strong, musky odor of ambrettolide. It is a volatile oil obtained by steam distillation from the partially dried and crushed seeds of the plant Abeltnoschus moschatus Moench, syn. Hibiscus abeltnoschus L. (Fam. Malvaceae). It is refined by solvent extraction to remove fatty acids or by precipitation of the fatty acid salts. It is soluble in most fixed oils and in mineral oil, often with cloudiness, but relatively insoluble in glycerin and in propylene glycol. 

The first documented fatty acid separation was reported by Guesserow (2). Separation of linear saturated fatty acids from linear unsaturated fatty acids by first preparing the lead salt derivative, dissolving the mixed salts in diethyl ether or ethyl alcohol, and then separating the less soluble saturated acids from the more soluble unsaturated acids has been reported. This was a very efficient method and involved large amounts of solvent and pre-preparation of fatty acid salts that made this process difficult to adopt in commercial scale (3). The classic commercial process of... 

Solubility differences of fatty acid salts In 1828, Gusserow introduced a method that lead salts or soaps of fatty acids in ether can be separated depending on the solubility differences. Saturated and unsaturated fatty acids form salts with metallic ions (e.g., Li) whose solubihties in water and organic solvents vary with the nature of the metallic ion and the chain length, degree of unsaturation, and other characteristics of the acid radicals. Substitution of ethanol for diethyl ether (113) allows better separation. 

Therefore, concentration of co3 fatty acids from PUFA-rich oils in the form of fatty acid salts may be achieved by employing a lower alcohol using solubility differences of the salts. In order to obtain high content of total co-3 fatty acid with a good recovery, the water content of the medium should be maintained at a 3% level. Han et al. (114) were able to increase the total co3 fatty acids of sardine oil from 33.2% to 75.9%. 

The simplest and most common synkinons are non-branched, saturated fatty acids from C12 to C18 (trivial names lauroyl Cl2, myristoyl Cl4, palmitoyl or cetyl Cl 6, stearoyl Cl8) and their sodium, ammonium and potassium salts (also known as soaps ). Laurie, myristic, palmitic and stearic acids are barely soluble in water at 20°C (5.5, 2.0,0.7 and 0.3 mg/L) and 60°C (8.7, 3.4, 1.2 and 0.5 mg/L), each ethylene group lowering the solubility by a factor of 2-3. The solubilities of the corresponding sodium and potassium salts are, however, in the order of several grams per litre. Even in highly concentrated emulsions of soaps in distilled water ( 30% w/w), precipitation of solids is often not observed. Bivalent fatty acid salts, however, are just as insoluble as free fatty acids only 1.4 mg of calcium stearate dissolves in 1 L of water. ... 

By definition, a fatty acid is a carboxylic acid that contains twelve or more carbons terminating in a carboxyl group. Because carboxyl groups disassociate at pH above 4-5, free fatty acids occur as negative carboxylate anions (R—COO ) in seawater and marine sediments. Although fatty acid salts are more water-soluble than hydrocarbons. 

The most important characteristic of hard water is its reaction with soap. If distilled or soft water be shaken with a solution of soap a lather or foam is formed immediately. If, however, a dilute solution of soap be added drop by drop to some hard water in a bottle which is stoppered and shaken after each addition, it will be found that no lather is formed at first. The water, at the same time, assumes a turbidity owing to the formation of an insoluble precipitate. Finally, after sufficient soap has been added, a lather will appear. Soaps are sodium salts of fatty acids of high molecular weight, such as sodium oleate CuHggCOONa. The salts of sodium are soluble in water, but those of calcium and magnesium are not and, in hard water, the ions of these elements displace the sodium, giving precipitates of their insoluble fatty acid salts ... 

Carboxylic acid salts are ionic substances. As a result, they are very soluble in water. The long-chain carboxylic acid salts (fatty acid salts) are called soaps. 

Surfactant Any substance that lowers the surface or interfacial tension of the medium in which it is dissolved. The substance does not have to be completely soluble and may lower surface or interfadal tension by spreading over the interface. Soaps (fatty acid salts containing at least eight carbon atoms) are surfactants. Detergents are surfactants or surfactant mixtures whose solutions have cleaning properties. Also referred to as surface-active agents or tensides. 

Mixtures of fatty acid salts are used as soaps. Sodium palmitate—stearate mixtures are solid at room temperature, and the corresponding potassium salt mixtures are fluid, although only potassium palmitate has been crystallized at room temperature. Metal carboxylates hydrolyze in water and release hydroxyl ions on the skin s surface. Soaps with fewer than 12 carbon atoms therefore bite. This happens with nonpurified soaps as obtained from fats containing fractions. Longer alkyl chains produce soft soaps, since they are not soluble as monomers in water and the surface liquids of the skin (sebum, sweat). Sulfonates, on the other hand, do not show such differences because they are always present as fully dissociated salts at physiological pH values and produce no hydroxyl ions. Allergic reactions to commercial soaps are mostly not caused by the fatty acids but by additives, such as perfumes. 

One undesirable property of soaps is their tendency to form precipitates with Ga, Mg, and Fe + ions found in hard water. The resulting fatty-acid salts of these doubly positive ions are not as soluble in water as the Na+ ion salts. These less-soluble molecules appear as a scum that sticks to laundry and bathtubs, often containing trapped dirt, which makes it appear even worse. 

The precipitation of soaps by polyvalent ions in aqueous solutions is considered to be troublesome in many applications. However, because metal soaps are soluble in organic solvents, mineral oils and fats, they are valuable additives in the production of plastics where they are used as mould-separation agents, emulsifiers and stabilizers. The fatty acid salts of lead and cobalt are used as siccatives in varnish and paints. 

Forming an optimal molding may require the addition of an external or internal lubricant to the formulation. Lubricants arc added in only small amounts, up to 1 wt %. External lubricants are insoluble in the phenohe matrix resin and are often non- polar materials such as parafiins and waxes. External lubricants act as mold release agents. In contrast, internal lubricants improve melt homogeneity, lower viscosity, and lower injection pressure. Therefore, internal lubricants such as fatty alcohols, fatty acid salts, acid esters, and acid amides must be fully soluble in the phenohe prepolymer [1]. 

There are two types of lipid-water phase diagrams. The first type, discussed above, is obtained from polar lipids, which are insoluble in water (i.e. the solubility is quite small, monolaurin for example has a solubility of about 10 m). Fig. 8.12 illustrates the principles of phase equilibria in this type of lipid-water system. The second type of binary system is obtained when the lipid is soluble as micelles in water. Examples of such lipids are fatty acid salts and lysolecithin. An aqueous soap system is illustrated in Fig. 8.13. When the lipid concentration in the micellar solution is increased, the spherical micelles are transformed into rod-shaped micelles. At still higher lipid concentrations the lipid cylinders are hexagonally arranged and the liquid-crystalline phase Hi is formed. The lamellar liquid-crystalline phase is usually formed in the region between Hi and the anhydrous lipid. Excellent reviews of the association behaviour of amphiphiles of this type have been published (Wennerstrom and Lindman, 1979 Lindman and Wennerstrom, 1980). 

In the beginning of past century, liquid soaps were prepared by dissolving potassium salt of coco fatty acids in glycerin [69]. With time, glycerin has been replaced by water, and fatty acid salts have been replaced by milder, more soluble, synthetic surfactants in liquid products. 

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