Tensio-active

With short chain derivatives, the forces of repulsion are higher than the ones of attraction the curvature is high and spherical micelles are formed at a concentration called the critical micellar concentration (cmc). This concentration can be detected by a change in the physico-chemical properties of the solution (e.g. surface tension, Fig. 3 a). Above a characteristic temperature (referred as Krafft temperature), the tensio-active molecules are infinitely soluble in the form of micelles (Fig. 3 b). 

Initial water solubility in the reactional medium is a key point, and two systems were designed to increase this parameter. The first solution is to use micro-emulsions of water in the solvent with the help af di-octyl-sulfosuccinate (AOT) as tensio-active agent, Good results can be obtained, but separation and recycling of the detergent are difficult to extrapolate at larger scales. 

In order to control this disadvantageous effect, de-foamers and de-aeraters are added19. The defoamer s task is to control the foam formation due to the tensio-active substances, while the de-aerater removes gas bubbles, in solution and in the fibre structure. In this way, the contact surface between fabric and bleaching solution is kept maximal, which can only favour the rate of the process. By adding the de-aerater, lower quantities of tensio-active substances are needed, which helps to minimise foam formation. 

Gloor, M. and B. Beier, Keratoplastic effect of salicyclic acid, sulfur and a tensio-active mixture. Z. Hautkr., 1984, 59 1657-60. 

Dissolution sensitive oL y and oSL values. Much stronger increases in R are expected from dissolution of a tensio-active species able to decrease significantly Csl and/or liquid volume is negligible. For example, for a droplet with 6y = 40°, a decrease of contact radius by a factor 2. 

Sometimes other variables must be investigated such as the pH and/or the ionic strength of the buffer in the mobile phase or the concentration of additives in the mobile phase such as for instance tensio-active substances in micellar chromatography. In such a case the first step in an optimization is to screen these factors and to identify the most important ones for the subsequent optimization. The screening (Section 6.4.2) leads to a definition of the experimental domain in which the optimum is probably situated. This is somewhat similar to the retention optimization step. It is followed by an optimization step (Sections 6.4 and 6.7), in which the most important variables are changed, often according to an experimental design. Similar methods are used in capillary zone electrophoresis. 

This method (Fig. 9.5 A) was set up to test, in aqueous medium and in the absence of substrate, the possible reactions between lipases and all the reagents to be tested [53, 54]. Residual lipase activity was measured separately using an emulsified substrate. Sometimes the inhibitor is incorporated into a solution of a tensio-active agent in order to create a mixed micellar interface, containing the incorporated inhibitor, and described as method A by Cudrey et al. [52]. 

The kinetics of hydrolysis of purified soybean oil (PSO) by the lipase were monitored by recording the interfacial tension decrease with time, using the oil drop tensiometer (ITConcept, France) as described by Nury et al. [58]. The interfacial tension was measured by automatically analysing the drop profile on-line, using the Laplace equation [59]. The accumulation with time of tensio-active components, i.e., lipolytic products, at the surface of an oil drop results in a decrease in the interfacial tension, which in turn is correlated with changes in the oil drop... 

Cases, J.M. (1979). Tensio-active adsorption at the sohd-liquid interface - Thermodynamics and influence of adsorbant heterogeneity. Bull. Minhalogie, 102, 684-707. 

Tensio-active Tyloxapol Make secretions less... 

The cleanliness of bottle waUs must be ensured by rigorous procedures (washing with tensio-active solutions, rinsing with dionized water, rinsing with acetone and hexane). The stopper materials that will come into contact with the extraction solvent must be chosen with care because... 

The main objective of this work consists in the direct catalytic synthesis of R2NCH3 or RN(CH3)2 dissymetricai tertiary amines, which find many applications in the industry of tensio-active products. To this end acids, esters, alcohols, nitriles obtained from triglycerides of natural origin can be used as raw materials. Starting from nitriles the following are the reactions to be performed... 

Determination of hydrophilic-lipophilic balances of some surfactants using tensio-active compoimds as stationary phases and injection of substances of suitable structure (normal hydrocarbons and alcohols) has also been recorded [126—127]. 

A most efficient test method for stress-crack resistance of bottles was established by Mitsui Petrochemical Industries Ltd. The MPC-H2-A 312-2/ 709 method consists of deforming filled bottles and immersing them in a tensio-active medium. 

The various facets of beer foam formation have been described by Bishop (101,108). The increased concentration of the iso-alpha acids in the foam could possibly lead to precipitation of metal isohumulates (in particular those of iron(ll), nickel(ll), cobalt(ll) and zinc(ll)), whereby the film around the air bubbles would be strenghtened leading to increased foam stability. This effect is probably reinforced by formation of complexes between the iso-alpha acids or their salts and proteins. It appears that such complexes only exist at sufficiently high concentration, i.e. at the surface of small air bubbles, when the beer starts foaming. The foam is stabilized by the tensio-activity of the complexes, which is more pronounced compared to that of the free acids (109). 

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