Stability of Lyophobic Suspensions

Particles in all kinds of suspensions or dispersions interact with two different kinds of forces (e.g., attractive forces and repulsive forces). One observes that, lyophobic suspensions (sols) must exhibit a maximum in repulsion energy in order to have a stable 

FIGURE 7.8 Variation of V(h) vs. h (a) stable (b) rapid coagulation (c) unstable. (See text for details.) 

After expanding these expressions, as related to h and C, this becomes (Schulze-Hardy Rule for suspensions in water) 

The flocculation concentrations of mono-, di-, and trivalent gegen ions should, from this theory, be expected as 

It thus becomes obvious that the colloidal stability of charged particles is dependent on 

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The strong adverse influence of calcium ions on the stability of lyophobic suspensions is predicted by DLVO theory, and has been demonstrated with many types of simple soils. That calcium ions have an overwhelming effect on the redeposition of carbon soil onto cotton tends to support the idea that DLVO theory is a principal key in explaining detersive action. The redeposition of carbon onto cotton has been correlated quantitatively with the calcium ion content of the system, both in the presence and absence of surfactant (95). The adverse effect of calcium ions on wet soil removal in practical washing has also been well established (96). The effect of calcium in detergency cannot be explained solely, however, by its shrinking of... 

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