Application of Solubility Soap

Soap has been used by humankind for some two thousand years. Historical records describe its manufacture in the first century and document the presence of a soap factory in Pompeii. Before this time clothes were cleaned by rubbing them on rocks in water, or by forming soapy lathers from the roots, bark, and leaves of certain plants. These plants produced natural materials called saponins, which act in much the same way as modern soaps. 

How does soap dissolve grease and oil Water alone cannot dissolve dirt, which is composed largely of nonpolar hydrocarbons. When soap is mixed with water, however, the nonpolar hydrocarbon tails dissolve the dirt in the interior of the micelle. The polar head of the soap remains on the surface of the micelle to interact with water. The nonpolar tails of the soap molecules are so well sealed off from the water by the polar head groups that the micelles are water soluble. 

When soap is dissolved in I-I2O, the molecules form micelles with the nonpolar tails in the interior and the polar heads on the surface. The polar heads are solvated by ion-dipole interactions with H2O molecules. 

Cross-section of a soap micelle with a grease particle dissolved in the interior 

Problem 3.14 Which of the following structures represent soaps Explain your answers. 

---

Suitable organic solvents, such as ether, benzene, naphtha and the like, are more soluble than in water. This makes it possible to separate them from other substances which may accompany them in the water solution but which are not soluble in the solvents employed. Hence, one application of solvent extraction is the analytical determination of unsaponifiable oils and waxes in admixture with fatty material by submitting the mixture to vigorous saponification with alcoholic potash or, if necessary, sodium ethylate, and to dilute the product with water and extract with petroleum ether. The soaps remain in the aqueous solution while the unsaponifiable oils and waxes dissolved in the ether. The addition of a salt to an aqueous solution prior to extraction is sometimes practiced in some processes. In older processes, SOj is employed in the separation of aromatic and highly saturated hydrocarbons, taking advantage of the much greater solubility of the solubility of the aromatics and... 

Composition vs. properties. One of the key properties of a soap, key to determining applications, is solubility. As with other surfactants, the solubility of the soap is dependent upon the carbon chain distribution, which is, in turn, determined by the choice of raw material oils. C12-14 gives a more soluble soap with very high foam generation whereas Ci8+ soaps have much reduced solubility. The use of unsaturated acids, such as oleic, gives improved solubility compared to the saturated equivalents and, where high solubility is required, potassium salt or an amine salt may be used instead of sodium salt. 

The greatest industrial consumption of monobasic aluminum acetate has been as a solution in the preparation of red color lakes for the dyeing of cotton. Formation of a water-resistant coating on fabrics, paper, leather, or other materials is also an important application. In this process, for example, cloth is dipped into a solution of water-soluble soap, then into the aluminum salt solution, forming an insoluble, water-resistant aluminum soap coating on the fiber surfaces (10). 

The oxyacids of pentavalent phosphorus are surprisingly numerous, and their chemistry is very complex. These considerations have only begun to be appreciated in recent years, when research has been stimulated by the discovery of important applications for the salts of these acids. The main application of the soluble phosphates is in water conditioning. Many of them possess the property of combining with calcium and magne- sium ions to form extremely stable soluble complexes that do not give precipitates with soap and do not deposit scale in boilers. Similar complexes are formed with iron, and stable soluble phosphates of iron find application in nutrition. Other uses for soluble phosphates are found in the textile industry, paints, and insecticide sprays. 

Tripropylene glycol Is a water-white liquid. One of its unique features is Its combination of water-solubility and good solubility for many organic compounds. Because of high boiling point and low volatility it is used in the formulation of textile soaps, lubricants, cutting oils, and similar applications. 

It had long been the desire of soap-makers to possess some process of saponification less tedious and costly than the ordinary systems of soap-boiling. It was well own that caustic alkalies would convert into saponaceous matter fats and oils, without the application of heat, and it was also well known that during the process of saponification by the ordinary system of boiling over caustic leys, a considerable amount of glycerine was set free, and which, being a substance soluble in water, passed away with the spent or waste leys, causing a direct and positive loss in the manufacture. 

---