Surfactant acid-soap complex

In soap bar processing free fatty acid is usually added in formulations to create so-called super-fatted soap. An acid-soap complex with a fixed stoichiometric ratio between alkaline soap and the fatty acid is formed. For example, the ratio of potassium acid soap is 1 1 while sodium soap forms acid soaps with various ratios. The fixed ratio complex exits not only in anhydrous crystalline phase but also in a hydrous liquid crystalline phase (11, 12). Oleic acid and its potassium soap form a 1 1 complex acid soap when equal molar acid and soap are mixed. Above the Krafft boundary, the acid soap in water forms a lamellar liquid crystal phase at low surfactant concentration, from a few percent, and the lamellar liquid crystal phase extends to ca 60% surfactant concentration. A hexagonal liquid crystal phase is formed after the lamellar liquid crystal phase with further increasing the surfactant concentration. This phase behavior is different from the soap and water phase behavior, in which the hexagonal liquid crystalline phase is formed first followed by the lamellar liquid crystalline phase. Below the Krafft boundary the acid soap complex forms a solid crystal and separates from water (4). 

The adsorbed layer at G—L or S—L surfaces ia practical surfactant systems may have a complex composition. The adsorbed molecules or ions may be close-packed forming almost a condensed film with solvent molecules virtually excluded from the surface, or widely spaced and behave somewhat like a two-dimensional gas. The adsorbed film may be multilayer rather than monolayer. Counterions are sometimes present with the surfactant ia the adsorbed layer. Mixed moaolayers are known that iavolve molecular complexes, eg, oae-to-oae complexes of fatty alcohol sulfates with fatty alcohols (10), as well as complexes betweea fatty acids and fatty acid soaps (11). Competitive or preferential adsorption between multiple solutes at G—L and L—L iaterfaces is an important effect ia foaming, foam stabiLizatioa, and defoaming (see Defoamers). 

This happens when the pH of the acid-soap system is lower than the pH of the amine-salt systems. This is the case of Fig. 17, if the two pH scales are assumed to be coincident. For some intermediate pH both systems exhibit a WI phase behavior, that is to say that they contain a high percentage of the corresponding ionized species. If both the acid and amine are placed in the same system at such a pH, the two ionic species would combine to produce a catanionic one, in equilibrium with the nonionic acid and amine species. Therefore, five surfactants would be present in the system, with relative proportions directly linked to the pH through the dissociation equilibria, the partitioning equilibria, and the catanionic association equilibriiun. How the phase behavior is altered by the pH through this complex scheme, does not seem easy to deduce and an experimental approach is surely the safer one. 

Various associative interactions of hydrolyzable surfactants in aqueous media can play a significant role in determining the adsorption behavior of these surfactants. For example, existence of ionomolecular complexes has been shown to have a significant effect on the adsorption of oleic acid on hematite as indicated by the flotation results (Xiao, 1990). Evidence for high surface activity of mixed acid-soap was obtained by surface tension measurements of oleate solutions (Ananthapadmanabhan, 1980). The surface activity of acid-soap was estimated to be larger than that of both the corresponding acid molecule and ionic soap. Similarly maximum flotation of quartz with alkylamine observed around pH... 

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". 

These surfactants, in conjunction with soap, produce bars that may possess superior lathering and rinsing in hard water, greater lather stabiUty, and improved skin effects. Beauty and skin care bars are becoming very complex formulations. A review of the Hterature clearly demonstrates the complexity of these very mild formulations, where it is not uncommon to find a mixture of synthetic surfactants, each of which is specifically added to modify various properties of the product. Eor example, one approach commonly reported is to blend a low level of soap (for product firmness), a mild primary surfactant (such as sodium cocoyl isethionate), a high lathering or lather-boosting cosurfactant, eg, cocamidopropyl betaine or AGS, and potentially an emollient like stearic acid (27). Such benefits come at a cost to the consumer because these materials are considerably more expensive than simple soaps. 

The solubihty characteristics of sodium acyl isethionates allow them to be used in synthetic detergent (syndet) bars. Complex blends of an isethionate and various soaps, free fatty acids, and small amounts of other surfactants reportedly are essentially nonirritant skin cleansers (66). As a rule, the more detersive surfactants, for example alkyl sulfates, a-olefin sulfonates, and alkylaryl sulfonates, are used in limited amounts in skin cleansers. Most skin cleansers are compounded to leave an emollient residue on the skin after rinsing with water. Free fatty acids, alkyl betaines, and some compatible cationic or quaternary compounds have been found to be especially useful. A mildly acidic environment on the skin helps control the growth of resident microbial species. Detergent-based skin cleansers can be formulated with abrasives to remove scaly or hard-to-remove materials from the skin. 

Red wine contains a surfactant that cleanses your mouth, removing fat deposits, re-exposing your taste buds, and allowing you to savor the next bite of red meat almost as well as the first bite. The tannic acid (also called tannin) in red wine provides a soap-like action. Like soap, tannic acid consists of both a nonpolar complex hydrocarbon part as well as a polar... 

The preceding four types of consumption mnst be determined experimentally in the laboratory and upscaled to field scales. The experimental conditions should be as close to the field conditions as possible. Field oil and water samples can be obtained, and experiments shonld be condncted at the held temperature. Ideally, reservoir rocks should be used. In practice, we may not be able to conduct all the necessary experiments becanse of the cost, available resources, and limited time. An approximation mnst be made to estimate the consumption for each type. For example, the consnmption for alkali reaction with crude oil can be estimated from Eq. 10.12, assnming all the acidic components are consumed to react with the alkali. The alkali consumption ACo in meq/mL is the same as the soap generated. ACo is generally a small fraction of the total consumption. Because these consumptions involve complex chemical reactions, efforts have been made to collect some published experimental data and were presented earlier. A general rule is 0.05 to 2% alkali concentration and 0.1 to 0.23 PV injection volnme. Note that alkali addition in an ASP system can rednce snrfactant and polymer adsorption. However, addition of snrfactant and/or polymer does not affect alkali consumption (Li, 2007). This is probably because the alkali molecules are smaller than the surfactant or polymer molecules, thus the existence of snrfactant and polymer molecnles will not affect the adsorption of alkali molecnles, nor will their existence affect alkahne reactions. 

Body washes are another more recent introduction into the marketplace. These products have become a mainstay in the global market. Body washes can be simple formulas similar to those used for liquid handsoaps or complex 2-in-l oil-in-water emulsion, moisturizing formulations. These products contain a wide range of synthetic surfactants not typically found in bar soaps or liquid handsoaps, such as sodium monoalkyl phosphate and alkyl aminocarboxylates. It is not uncommon to find over 20 different components in these formulations, with no less than six or seven different surfactants. These products can also contain skin benefit agents, such as cholesterol, fatty alcohols, fatty acids, cationic polymers, and emollient oils to provide even milder-to-skin cleansing and in-use moisturization. 

Patel and Patel (1999) proposed a FIA-spectrophotometric method that enables Ci2 i6 trimethylammonium and cetylpyridinium chloride to be determined by means of forming a complex between the cationic surfactants and Fe (III)-SCN. The effect of FIA variables on determining surfactant in nitric acid medium was studied however, possible interferences (ions present in formulation) were not encountered. This method of determining cetylpyridinium chloride in soap and shampoo was compared with an established FIA method, in which the complex was formed with an anionic dye (Orange II), and the former method attained better sensitivity, selectivity and reproducibility. 

The primary reaction of a flux (acid) with a metal oxide (base) is to form a salt at the surface of the solder, and water that is evolved with heat during reflow. A study of the reaction products of abietic acid with SnO, PbO, and CuO identified carboxylate salts [152]. It should be emphasized that the product of this reaction is an organic salt, and should not be referred to as a complex to distinguish it from coordination complexes. The salt acts as a surfactant (i.e., it lowers the surface tension of the liquid solder, much as soap lowers the surface tension of water, and promotes the reaction of the metals). 

The tall oil soaps are particularly attractive because they are very inexpensive. They are actually complex mixtures of fatty acids and rosin acids, which are difficult to characterize and control. The presence of the rosin acids in these materials generally imparts better water solubility as well as enhanced surfactant properties. Because of their complex nature and difficulties in obtaining sufficiently clean materials, the tall oil soaps have generally found use only in the most tolerant areas of heavy-duty industrial cleaning and within the processes from which they are derived. 

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