Solid phases, soaps

Small molecule size-c Ecluslon chrmutography 441 Soap-film meter (GC) 4, 235 Solid-phase extraction 777 cartridges 777 membranes 780 optimization 777, 783 sorbents 778, 785 trace enrichment 777, 783 Solubility parameters 460 Solvatochromic parameters GC 191... 

Solid-phase reagents, 12 136 Solid-phase regrowth (SPR), in compound semiconductor processing, 22 190 Solid phases, soap, 22 728-731 Solid-Phase Synthesis database, 6 20 Solid polymer electrolyte (SPE) process,... 

It is an everyday experience that calcium soaps have a low aqueous solubility while many surfactants with monovalent counterions have an extremely high solubility. As for other compounds, the solubility is to a great extent given by conditions in the solid phase, but for surfactants the strongly cooperative association produces the peculiar temperature dependence of solubility schematized in Fig. 2.8. The so-... 

Pneumatic Conveying Dryers A gas-solids contacting operation in which the solids phase exists in a dilute condition is termed a dispersion system. It is often called a pneumatic system because, in most cases, the quantity and velocity of the gas are sufficient to lift and convey the solids against the forces of gravity and friction. (These systems are sometimes incorrectly called flash dryers when in fact the moisture is not actually flashed off. True flash dryers are sometimes used for soap drying to describe moisture removal when pressure is... 

Fig. 1. The fatty acid soap-water phase diagram of McBain (58) modified (1) to show the molecular arrangement in relation to aqueous concentration (abscissa) and temperature (ordinate). Ideal solution, i.e., true molecular solution, is to the left of the vertical dashed line, indicating the critical micellar concentration (CMC), which varies little with temperature. At concentrations above the CMC, provided that the temperature is above the critical micellar temperature (CMT), a micellar phase is present. At high concentrations, the soap exists in a liquid crystalline arrangement, provided that the solution is above the transition temperature of the system, i.e., the temperature at which a crystalline phase becomes liquid crystalline. The Krafft point is best defined (D. M. Small, personal communication) as the triple point, i.e., the concentration and temperature at which the three phases (true solution, micelles, and solid crystals) coexist, but in the past the Krafft point has been equated with the CMT. The diagram emphasizes the requirement for micelle formation (a) a concentration above the CMC, (b) temperature above the CMT, and (c) a concentration below that at which the transition from micelles to liquid crystals occurs. Modified from Hofmann and Small (1).

There is plenty of information available in literature on liquid crystalline and isotropic phases of different surfactants, but the study of the solid phases is limited to only soaps [12-19]. The basic reason for the lack of solid phase studies of synthetic surfactants is their limited use in solid form. The low KP of these surfactants limits their use to liquid products. Owing to a relatively high KP, sodium cocoyl isethionate (SCI), alkyl glycerol ether sulfonate (AGES), and sodium cocoyl monoglyceride sulfate (CMOS) form solid phases at room temperature, but there is hardly any information available on these solid phases. 

A substantial amount of work has been carried out on thermotropic transitions of anhydrous soaps and other surfactants using high-temperature XRD and NMR. The mobility of the hydrocarbon chains increases with temperature, which leads to the formation of mobile solid phases (waxy phases) and liquid aystalline phases [27-29], These transitions have very limited application in cleansing products. Some of these transitions take place during processing of soap at elevated temperatures. 

De Mul MNG, Davis HT, Evans DF, Bhave AV, Wagner JR (2000) Solution phase behavior and solid phase structure of long-chain sodium soap mixtures. Langmuir 16 8276-8284... 

This means a very low T. For a soap solution, is near room temperature. Polymer soap forms solid phases at room temperature, giving curd stabilized by a hydrated layer. When a polymer particle is uniform in size, curd are of regular structurelike crystal developing rainbow colors [28a]. 

The CH2 wag bands in CH2 chains are spread over a region because of CH2—CH2 wag interaction (see Fig. 4.14). They can be most clearly seen in the solid phase spectra of long straight chain compounds such as fatty acids and soaps. In Fig. 5.8 a series of sharp regularly spaced bands can... 

Addition of small quantities of electrolyte and perfume can also influence the liquid and solid-phase ratio. Electrolyte reduces the soap solubility and therefore increasing the solid-phase amount while perfume increases the soluble soap amount. 

The phase changes during the hydration process involve the dissolution of the eta type solid-phase phases to form additional liquid crystal and solution phases. The less soluble kappa phases that contain longer chain soaps also dissolve and the long chain soaps then reprecipitate as insoluble solids. These solids along with the liquid crystalline phases are responsible for the mush layer which forms on the bar surface. 

Some substances exist in more than one liquid form liquid crystals or anisotropic liquids, forming various types of mesomorphic phases (nematic, smectic, cholesteric). They share properties normally associated with both liquids and crystals. Sodium soaps have numerous mesomorphic states. Amorphous (metastable) phases of a substance may also display polymorphism. However, often the term polymorph is explicitly restricted to the solid phase and polymorphic transformations are restricted to transformations involving phases with different crystal structures which are part of a single component system such solid polymorphs form an identical liquid on melting. For example, phosphorous has many solid allotropes, which all revert to the same P4 form when melted to the liquid state. In contrast, for isomers the difference between them persists in the liquid phase. Polymorphs (allotropes) can be combined with other substances to give the same compounds isomers give different reaction products. 

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