| Popis: |
Experimentally determined stability coefficients for the coagulation of hematite dispersions consisting of uniform spherical particles, and for the deposition of the same solids on glass beads, are compared with theoretically predicted values by the Hogg, Healy and Fuerstenau (HHF) approximation and the recently developed Overbeek formulation. Significant discrepancies are found between the measured coefficients for slow processes and those calculated by either the HHF or the Overbeek expressions. The effect of the linearization incorporated in the HHF approximation on the computation of stability coefficients is also assessed by the comparison with the Overbeek treatment. It is found that considerable deviations are generated when Ψ S1 ≈ Ψ S2 > 25 mV, where Ψ S1 and Ψ S2 are the Stern potentials for surfaces 1 and 2 respectively, whereas good agreements ensue when Ψ S1 ⪡ Ψ S2 , even though Ψ S2 is as high as 100 mV. |
