Zeta potential worked example

Many investigators of steric stabilization have measured colloidal stability without taking the effort to find out whether the stability actually resulted from electrostatic stabilization. In many published articles it has been concluded that steric stabilization had been attained and further study showed this was not the case. One such example is a recent paper on "steric" stabilization by an additive of the same type used in this work. (12) The published photograph shows the silica particles in oil stabilized at interparticle separations several times the distances provided by the adsorbed films no electrical measurements had been made, but it they had, this particular dispersant would have provided about -200 mV of zeta-potential and given excellent electrostatic repulsion. The reader should be wary of any claims of steric stabilization unless the electrostatic contribution has been measured. 

Electro-osmosis is an important process in capillary electrophoresis. When the separation capillary is filled with a working electrolyte, an electric double layer is always formed on the inner wall surface due to ionizable groups of the capillary wall material and/or ions absorbed on to the capillary wall. For example, in quartz capillaries, the silanol groups present at the surface form the fixed negative part of the electric double layer. The positive part is then formed by ions present in the solution. A fraction of the ions forming the electrolyte part of the electric double layer is always fixed by electrostatic forces near the capillary wall and forms the so-called Stern layer the rest of these ions form, however, the mobile diffuse layer. The potential this creates between the Stern layer and the bulk solution is termed the zeta potential (in V), and is given by... 

A general conclusion has been reached that drilling rate is a maximum, wear rate a minimum, and hardness a maximum in any environment at a pH that produces a zeta potential equal to zero. Thus the isoelectronic point is important however it is achieved Figure 4.10 is a visual demonstration of this viewpoint taken from the work of Swain et Chemisorbed or weakly physisorbed species lead to differing effects for example, weakly absorbed lauric acid does not shift the zeta potential from pH = 9.0 (fixed by strongly adsorbed OH" and that between them determine the surface potential) while oleic acid is strongly chemisorbed and so the isoelectronic point moves to pH 7.5 and drilling rates and hardness are consequently affected. 

An understanding of the complex physico-chemical phenomena associated with the formation and behavior of cementitious compounds is facilitated through the application of many different types of investigative methods. Techniques such as NMR, XRD, neutron activation analysis, atomic absorption spectroscopy, IR/UV spectroscopy, electron microscopy, surface area techniques, pore characterization, zeta potential, vis-cometry, thermal analysis, etc., have been used with some success. Of the thermal analysis techniques the Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TG), Differential Scanning Calorimetry (DSC), and Conduction Calorimetric methods are more popularly used than others. They are more adaptable, easier to use, and yield important results in a short span of time. In this chapter the application of these techniques will be highlighted and some of the work reported utilizing other related methods will also be mentioned with typical examples. 

As demonstrated in our recent works [33-35], the CASCCSD wave function constructed in the above-described way provides in all studied cases a very accurate description of the potential energy curve (PEC) in comparison with FCI. Let us, for example, show in more details how the method performs in the case of the dissociation of the hydrogen fluoride (FH) molecule. The calculations have been performed with the standard valence double-zeta (DZV) basis set (implemented in GAMESS package [36]). The results are presented in Table 3.2. As one can see in Table 3.2, the differences between the CAS(2,2)CCSD and FCI energies are almost constant and small for all the PEC points shown in the table. The worst results... 

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