Solution velocity

Fig. 8. Effect of solution velocity on the growth rate of the < 110 > face of MgS04-7H2 0. Concentration of MgSO ...

Solution Velocity The effect of velocity is not usually determined in laboratory tests, although specific tests have been designed for this purpose. However, for the sake of reproducibility some velocity control is desirable. 

Figure 5.7 Effect of solution velocity on crystal growth rates after Miillin and Garside, 1967) number Sh = IcLjD, the partiele Reynolds number...

Dissolution is uniform (etching) otherwise, for rough surfaces such as pitting, turbulent flow regimes may occur even at low solution velocities. 

A striking example of the interaction of solution velocity and concentration is given by Zembura who found that for copper in aerated 0-1 N H2SO4, the controlling process was the oxygen reduction reaction and that up to 50°C, the slow step is the activation process for that reaction. At 75 C the process is now controlled by diffiision, and increasing solution velocity has a large effect on the corrosion rate (Fig. 2.5), but little effect at temperatures below 50 C. This study shows how unwise it is to separate these various... 

Thus the rate of change of ip under activation control is much faster than / i, which is under diffusion control, and for the same condition of solution velocity the two rates could become equal at some common temperature, i.e. = ip, and there is no active-passive transition. For many of the systems given in the table this temperature is about 100°C. Above this temperature the measured activation energy is lower and diffusion control is established. 

Separation by electrophoresis is based on differences in solute velocity in an electric field. The velocity of an ion is given by... 

It is further useful to measure ionic species in stirred or flowing solutions, because the electrode response is then faster, the determination limit is often better than in quiescent solutions and the measurement precision is also improved These improvements apparently result from the effect of solution movement on film diffusion at the electrode surface, which is assumed to be the response-rate determining step [92, 154], An obvious requirement is that the solution velocity and the cell geometry be constant. 

The electrophoretic separation principle is based on the velocity differences of charged solute species moving in an applied electric field. The direction and velocity of that movement are determined by the sum of two vector components, the migration and the electroosmotic flow (EOF). The solute velocity v is represented as the product of the electric field strength E and the sum of ionic mobility uUm and EOF coefficient /a OF ... 

Effect of Solution Velocity 1.18 -1.21 g. LiaCOj/IOOfl. solution Wall temperature 179.8 - I80.5 F... 

Calcium Sulfate Effect of Solution Velocity 0.II g. CaS04/l00 ml. solution... 

Interactions between solutes and tissue structures will retard the convective transport of solutes. Thus, the solute velocity is always smaller than the fluid velocity during convection. The ratio of the velocities is... 

The boundary layer thickness 8 in Equation (4.11) is a function of the feed solution velocity u in the module feed flow channel thus, the term 8/D, can be expressed as... 

The retardation factors of the four radioelements for four hypothetical HLW compositions were derived using the prediction equations. (The retardation factor is the ratio of the solution velocity to the radioelement velocity in a system of solution flow through a porous medium and increases linearly with Kd.) The four hypothetical HLW solutions broadly represented dilute/non-complexed, dilute/complexed, concentrated/noncomplexed, and concentrated/complexed HLW. Dilute waste had low concentrations while concentrated waste had high concentrations of Na+, NaOH, and NaAlO,. Non-complexed waste had no HEDTA or EDTA while complexed waste had 0.1M HEDTA/0.05M EDTA. 

These four equations form the basis for a description of the mass transport in electrolytic solutions. To solve these equations, we must calculate the bulk solution velocity from a knowledge of the fluid mechanics. 

Factors leading to non-Gaussian zones in separation systems were described generally in Section 5.9. One source of zone asymmetry identified was the variation of local solute velocity W with solute concentration, described as overloading. The way in which overloading causes zone asymmetry in chromatography is explained below. 

In accord with the earlier discussion, zone broadening occurs because solute velocity at the front and back of the zone is such as to pull these parts further and further from the center. An instructive way to look at this is to note that when Acm is positive, as it is ahead of center, solute in amounts greater than the equilibrium value are being transported through each unit area of column in each second. That is, with respect to equilibrium, extra solute in proportion to Acm is transported forward thus solute at the front of the zone is out-pacing all other solute. At the rear, with Acm negative, solute transport falls behind. Thus the zone spreads out. 

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