Primary equilibrium

The pH is governed by the major solute species present in solution. As strong base is added to a solution of a weak acid, a salt of the conjugate base of the weak acid is formed. This salt affects the pH and needs to be taken into account, as in a buffer solution. Table 11.2 outlines the regions encountered during a titration and the primary equilibrium to consider in each region. 

A nonunity ratio (sometimes called a thermodynamic isotope effect) of the equilibrium constants ( ught/ heavy) for two reactions differing only in the isotopic composition at one or more positions of their otherwise chemically identical substances . If the equilibrium isotope effect is attributable to a covalent bond making/breaking, then the effect is often referred to as a primary equilibrium isotope effect. If isotopic substitution at a position other than the scissile bond results in an equilibrium isotope effect, the term secondary equilibrium istope effect is used. 

Primary equilibrium in the chromatographic system is the analyte distribution between mobile phase and the surface of packing material. If the analyte could be present in the mobile or stationary phase in two or more different forms and there is an equilibria between these forms, this equilibria is usually called secondary. ... 

Certainly one of the major advantages of the aqueous-based mobile phases used in reversed-phase liquid chromatography is the ability to control secondary chemical equilibria. In liquid chromatography the primary equilibrium is the distribution of the solute between the stationary and mobile phases. Any other equilibrium involving the solute in the mobile or stationary phases is considered secondary. These secondary equilibrium processes change the chemical form of the solute, and can be used advantageously to change retention of solutes that... 

Equation (3.12) clearly shows the dependence of the distribution ratio on the secondary equilibrium (i.e., the weak acid dissociation,) and on the extent of the primary equilibrium (i.e., the partitioning equilibrium of molecular HO Ac between two immiscible phases). If Eq. (3.12) is rearranged, we get... 

Alternatively, Eq. (3.12) can be viewed in terms of the primary equilibrium as represented by Kj) and in terms of secondary equilibrium as represented by mhoac- Let us define mhoac the fraction of neutral or undissociated HOAc present according to... 

Three-dimensional (3-D) plot of the shape memory cycle for (a) a shape memory polymer (SMP) and (b) vulcanized natural rubber. The star indicates the start of the experiment (initial sample dimensions, temperature, and load). Both the SMP and the rubber were deformed under constant loading rate at constant temperature. The deformation step was then followed by a cooling step under constant load. At low temperature, the load was removed and shape fixing was observed for the SMP, but an instant recovery was seen for natural rubber. Shape recovery of the primary equilibrium shape was obtained by heating the SMP. (Adapted from Liu, C., Qin, H., and Mather, P. T. 2007. Review of progress in shape-memory polymers, journal of Materials Chemistry 17 1543-1558. Copyright Royal Society of Chemistry. Reproduced with permission.)... 

The chloroaluminate ionic hquid mixtures are governed by the following primary equilibrium, equation ... 

The basic mechanism of separation in MLC is fairly well understood and there is a reasonable theoretical foundation on which to build. MLC is a fascinating example of the use of a secondary chemical equilibrium in liquid chromatography. The primary equilibrium is the partitioning of the solute between bulk mobile phase and stationary phase, and the secondary equilibrium is the partitioning to micelles. This secondary equilibrium is affected by a great variety of parameters type and eoncentrations of surfactant and additives such as salts or organic modifiers (for instance, alcohols), and pH. The current knowledge on MLC interactions is exposed... 

The conversion of H2S and the recovery of sulfur is one of the more simple chemical reactions that takes place in a refinery. First, an aqueous solution of amine, which is an organic base, scrubs H2S and COt out of a hydrocarbon stream. Then the acid gas (H2S plus CO2) is stripped out of the amine with steam. The acid gas is charged to the sulfur plant where the H2S is partially oxidized to water and sulfur according to the primary equilibrium reaction ... 

As a result of thermodynamic fluctuations or outer disturbances, the surfaces of a thinning liquid film are corrugated (see Fig. 33d). When the derivative of the disjoining pressure, dU/dh, is positive, the amplitude of the film surface corrugations spontaneously grows with the decrease of the film thickness [5,6,420,492]. The appearance of unstable fluctuations is possible even in the relatively thick primary equilibrium films as a result of fluctuations in the electric potential [6,493]. The evaporation dr condensation of solvent... 

This is a notably simple result, immediately available for any fluidized system. It has the same form as that proposed by Wallis (1962) on the basis of fluid-dynamic scaling considerations. The fact that the primary equilibrium force expression employed in the derivation, eqn (6.7), applies regardless of the flow regime provides for more generality than earlier formulations of stability criteria that assumed creeping flow conditions (Molerus, 1967 Verloop and Heertjes, 1970). 

The retention of an eluite in liquid chromatography is based upon the distribution of the eluite between the stationary and mobile phase (primary equilibrium). By convention, any other equilibria that takes place in the mobile phase, or stationary phase, or both, are considered secondary . In the past, manipulation of the mobile-stationary phase equilibrium distribution of the solute by using secondary chemical equilibria (SCE) was widely utilized in order to overcome low column efficiencies [32]. In spite of the fact that we now have columns with higher inherent efficiencies, SCE is still a widely practiced technique. The wide range of different chemistries that can be used to alter the mobile-stationary phase equilibrium to achieve better resolution or... 

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