Activity, definition solubility product

Activity Coefficients from Solubility Measurements.—The activity coefficient of a sparingly soluble salt can be determined in the presence of other electrolytes by making use of the solubility product principle. In addition to the equations already given, this principle may be stated in still another form by introducing the definition of the mean ionic concentration, i.e., c , which is equal to c+clr, into equation (109) this equation then becomes... 

Is called the solubility product of the salt. (It should be noted that it IS not customary to extend this definition to hydrated salts, but there is no reason why they should be excluded.) Values of the solubility product are often given on mole fraction or concentration scales. In dilute solutions, the theoretical behaviour of the activity coefficients as a function of ionic strength is often sufficiently well known that reliable extrapolations to infinite dilution can be made, and values of Kg can be determined. In more concentrated solutions, the same problems with activity coefficients that were outlined in the section on variation of solubility with temperature still occur. If these complications do not arise, the solubility of a hydrate salt CvAv nH20 in the presence of other solutes is given by eqn [SO] as... 

The saturation of water refers to the solubility product of a compound. By definition, the ion-activity product (lAP) of reactants—i.e., Oca2+ and 00032- when CaCOs is the sealant—is, at equilibrium, equal to K,p-. 

The SL definition can be simplified if the activity coefficients are incorporated into the solubility product in order to use a more practical concentration unit. The conditional solubility product incorporates the activity coefficients into the solubility product. 

The polymerization of diphenyldiacetylene in the presence of vanadyl acetyl-acetonate and triethylaluminum gave an open-chain polymer 10) [13]. However, when tri(isobutyl)aluminum and titanium tetrachloride were used to catalyze polymerization of [11], the product was postulated to contain another type of repeat unit [14] 35). The soluble product from the latter polymerization possessed a cryoscopic molecular weight of 1270 and a softening point of 255°-260°C. It also had good heat resistance, losing only 3% of its weight after 6 hours at 250°C in argon. Definite catalytic activity toward the decomposition of nitrous oxide was exhibited by this product [12,14]. 

There are cytosolic and membrane-bound isoforms of NO synthase. Certain soluble and particulate isoforms are constitutive and other soluble isoforms are inducible. The constitutive enzyme is, by definition, present in the catalytically active form and needs only to be stimulated by an appropriate chemical species, following which there is immediate formation of NO plus L-citrulline. This form of NO synthase requires calcium, and for the most part calmodulin, for stimulation of enzymatic activity. It is likely that an increase in intracellular free calcium in the presence of calmodulin is the signal for stimulation of NO synthase, and therefore, the production of NO. This view is consistent with the general understanding that, in vascular tissue, all endothelium-dependent vaso-... 

Surfactants. By definition every detergent product contains one or more types of surfactants. Basically, every surfactant is an organic compound consisting of two parts (I) a hydrophobic portion, normally including a long hydrocarbon chain, and (2) a hydrophilic portion, which renders the entire compound sufficiently soluble or dispersible in water or other polar solvent to serve its intended use. Together, these combined hydrophobic and hydrophilic moieties render the compound surface-active—able to concentrate at the interface between a surfactant solution and another phase, such as air. soil, and textile substrate to be cleaned. 

The natural substrates for lipases are triglycerides but, because of the complexity of these and the fact that they seldom contain a chromophore or other label to enable ready detection of the products, several synthetic substrates have been developed. These enable different detection techniques such as spectrophotometry, fluorimetry, chromatography, or radiometry to be used. It is important to note that, by definition, true lipases are active only on water-insoluble esters while esterases cleave only water-soluble esters (Jaeger et al., 1994). Thus, it is important that methods used for milk and milk products use substrates, which detect true lipase but not esterases as lipases play a major role in the hydrolysis of milk fat, while the role of esterases is considered insignificant (McKay et al., 1995). 

In this procedure the diphosphine intermediate serves as the basis for the elaboration of a water-soluble rhodium-based homogeneous hydrogenation catalyst. The enantioselectivity of the catalyst was tested by the reduction of a-acetamidoacrylic acid to iV-acetylalanine. The presence of avidin resulted in a definite increase in activity of the catalyst and in the production of the S-enantiomer (natural amino acid) in 40% excess. 

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