Short chain soaps

We have carried out similar experiments with saturated fatty acid soaps as the first soap and bile acids (as the sodium salt) as the second soap (66). The bile acids behave as typical ionic detergents with critical micellar temperatures well below 0°C (Fig. 10). For any saturated fatty acid soap, its critical micellar temperature decreases as the chain length shortens. Thus, at 37°C, more of a short-chain soap will be solubilized for a given amount of bile acid present, or, to paraphrase, the molar ratio of soap/bile acid will be much higher for short-chain soaps at 37°C. One carries out these experiments by incubating a series of different molar ratios of soap/bile acid. The bile acid is micellar, and the soap is crystalline. Over a few degrees of temperature range, the crystalline soap completely dissolves. No satisfactory quantitative description of these experiments has, as yet, been proposed. 

Lather volume depends upon the amount and the type of soap dissolved in the soap liquor during lathering. The mobility of the soap molecules, in addition to their surface properties, contributes to foaming. It is therefore possible that the soaps with very short chains (sodium caprylate and sodium caprate) may have an additional lather benefit. However, the proposed benefit should be restricted to low wash temperatures. The source of the short chain soaps is the coconut or palm kernel oil component of the fat charge. The amount of soap in solution in the wash liquor increases as the level of soluble soap in the bar increases. However, because the lather depends on the very short transient hydration period, it is the amount of soap which goes into solution over this period that is important. This amount also increases as the rates of dissolution of the solid soluble phases of the bar structure increase. 

Sulfated Acids, Amides, and Esters. Reaction with sulfuric acid may be carried out on fatty acids, alkanolamides, and short-chain esters of fatty acids. The disodium salt of sulfated oleic acid is a textile additive and an effective lime soap dispersant. A typical sulfated alkanolamide stmcture is CiiH23C0NHCH2CH20S03Na. Others include the sulfates of mono and diethanolamides of fatty acids in the detergent range. The presence of... 

The anion used to prepare the metal soap determines to a large extent whether it will meet fundamental requirements, which can be summed up as follows solubihty and stabiUty ia various kiads of vehicles (this excludes the use of short-chain acids) good storage stabiUty low viscosity, making handling the material easier optimal catalytic effect and best cost/performance ratio. 

Sulfonates include alkylbenzenesufonates (ABS), the most widely used of the non-soap surfactants short-chain alkylarenesuifonates lig-nosulfoliates napllialenesulfoliates cz-olefinsulfonales petroleum sulfonates sulfonates with ester, amide, and ether linkages and fatty acid ester sulfonates. 

Soaps Short-chain saturated fatty acids, particularly C12 (lauric) from coconut, are used in cosmetic soap manufacture. Though there has been interest in developing Cuphea species as a source of C12 fatty acids in temperate northern latitudes, it has proved difficult to commercialise to date. 

The total concentration of free fatty acids is usually determined by extrac-tion/titration methods or spectrophotometrically as Cu soaps. Early attempts to quantify the concentration of individual short-chain fatty acids involved steam distillation and adsorption chromatography. Complete separation and quantitation of free fatty acids can be achieved by GC, usually as their methyl esters, for which several preparative techniques have been published. Free fatty acids are major contributors to the flavor of some varieties, e.g., Romano, Feta, and Blue in the latter, up to 25% of the total fatty acids may be in the free form. Short chain fatty acids are important contributors to cheese aroma, while longer chain acids contribute to taste. Excessive concentrations of either cause off-flavors (rancidity) and the critical concentration is quite low in many varieties, e.g., Cheddar and Gouda. 

Long-chain alkanoic acids have a limited use as surfactants. They are very weak acids having a pH range between 5 and 6. They are soluble in most organic solvents but purely soluble in water. Alkali metals and short-chain amines as counterions yield water-soluble soaps which, as a result of hydrolysis, form with free acids the dispersible 1 1 or 1 2 association complexes, so-called "acid soaps". 

It is interesting to note that the mesomorphic behavior of these lanthanides carboxylates is much closer to the behavior of alkaline and alkaline earth soaps than to the transition metal soaps described above. However, it is less complex since only one smectic A mesophase is observed, although sometimes a second mesophase, which has not been identified by X-ray diffraction, is present for the short-chain homologs. Such a simple behavior has been attributed to the high carboxylate-to-metal ratio, which makes the ionic layer more rigid. 

A major use is in soaps because lauric acid imparts excellent solubility and lathering properties. Palmkernel acids are also used to produce short-chain alcohols and their derivatives for detergents. Edible uses include margarine, ice cream and biscuit cream fillings. The melting behaviour of palmkernel and coconut oils are compared in Table 3.30. 

The choice of a specific mixture will affect the quality of the final soap. [For example, short-chain fatty acids are more soluble they yield soaps, which despite giving out more foam are also more irritating for the skin and wear out faster.] A compromise must be found to get a mixture that satisfies the desired performances and cost criteria [3]. 

An alternative method of separation is to sorb all the anions on a strongly basic anion exchanger hydroxide and to elute the short-chain sulphonates with at least 30 bed-volumes of 1 M aqueous hydrochloric acid. If soap is present, elute the fatty acids first with at least 12 bed-volumes of 1 M ethanolic acetic acid, followed by a wash with 5 bed-volumes of water. 

Dissociated fatty acids (soaps) have quite different features. Delocalisation of the C=0 double bond across the CO2 group depresses the frequency of the stretching vibration. Stretching of the two C-O bonds is coupled (i.e. the vibration of one influences the vibration of the other). Both asymmetric and symmetric vibrations occur and are infrared active. Bands appear between 1600 and 1560 cm (asymmetric), and 1420 and 1340 cm (symmetric), with short-chain carboxylates absorbing at the higher end of the range. 

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