Viscosity of medium

The electrokinetic effect is one of the few experimental methods for estimating double-layer potentials. If two electrodes are placed in a coUoidal suspension, and a voltage is impressed across them, the particles move toward the electrode of opposite charge. For nonconducting soHd spherical particles, the equation controlling this motion is presented below, where u = velocity of particles Tf = viscosity of medium V = applied field, F/cm ... 

Although all theoretical approaches discussed in previous sections do refer to a particular molecular model, rather they represent attempts to rationalize experimental kinetic data in terms of mean values of electrical field or ion distribution, energy barrier height, energy change, ion mobility and viscosity of medium, which are all supposed to be closely related to the molecular properties of the ions and solvent molecules involved. However, no direct link to molecular properties has been established within the framework of the models discussed above. 

Hxcept for preliminary culculalions that indicate that they can operate its described here (102], these proposed effects tire not yel supported by additional information. However, there are other possible links to known facts. (1) Perhaps two-phase effects could explain why the lits of D-model calculations are belter for solvents DF.F and THF than for solvents DBF. and DPL (Section 7.2.8). (2) A high viscosity of medium adjacent to Mg/, sufficient to slow the rotation of R-. could result in partial retention of configuration (Section 7.2.9), provided that the value of <5 were not decreased as well. 

If the initiator concentration used in a free-radical polymerization system is low and insufficient, leading to a large depletion or complete consumption of the initiator before maximum conversion of monomer to polymer is accomplished, it is quite likely to observe a limiting conversion poo which is less than the maximum possible conversion pc, as shown in Fig. 6.2. This is known as the dead-end effect and it occurs when the initiator concentration decreases to such a low value that the half-life of the kinetic chains approximates that of the initiator. However, if there is autoacceleration effect or gel effect (described later) leading to a sharp rise in rate of polymerization, viscosity of medium, and degree of polymerization, pure dead-end effect cannot be observed. 

Equation (ni.3.24) indicates that ions with different radii must have different diffusion coefficients in the same medium and, consequently, different mobility (Eqs. III.3.19 and III.3.20) and conductivity (Eq. III.3.21). Moreover, Eqs. (in.3.21) and (III.3.24) show that the product of the equivalent conductivity of a certain electrolyte and the viscosity of medium is approximately constant. This is the empirical Walden s mle, which applies if the radii of solvated ions in various media are not significantly different. 

Eq.(32) indicates that the relaxation time of the electrode polarization decreases with the number concentration of ions and increases witli the size of ions, the dielectric constant and the viscosity of medium. Detailed discussion on the electrode polarization will be given further on. 

In this case the second-order constant does not depend on particle size, only on temperature and the viscosity of medium. This rate constant often implies rapid colloid aggregation. 

Thus, on the basis of the analysis set forth above, it is possible to assert that decrease in general efficiency of a dust separation at excess of boundary concentration of slurry is connected about all by decreasing ability of system to detain small corpuscles. Especially, it touches badly moistened corpuscles. It coincides with a hypothesis about updating of an interphase surface. Updating of an interphase surface can be coimected also with difficulties of motion of the settled corpuscles of a dust deep into liquids, i.e., with viscosity of medium. 

Viscosity of medium Take extra care when handling viscous media (pour along side of vessel pipette slowly, etc.) leave system for 1-2 hours (or overnight) with pump off to allow bubbles to rise to the surface or dissipate. 

---