Hiroki Yotsumoto

Estimation of Structural Force in Rutile Suspensions.

The DLVO theory has been used successfully to describe the stability of synthetic rutile suspensions in NaCl solutions of 2×10-3 M and below. At higher NaCl concentrations, the suspension is more stable than predicted by the theory. At concentrations above 1 M, the suspension is peptized even at its i. e. p.It is believed that the additional stability is due to the structural force not considered in the DLVO theory. The structural force can be described by a double exponential function, the parameters of which have been determined on the basis of turbidity measurement. It has been also tried to explain the additional stability of rutile suspensions at NaC1 concentrations 2×10-1 to 2×10-2 M by modifying the electrostatic interactions of the DLVO theory. However, the modification requires the irregular shift of shear plane position with pH and an unacceptable assumption that particles will not coagulate at the deep secondary minimum of potential energy curve. The additional stability of rutile suspensions can be reasonably explained by the structural force, but not by the electrostatic interactions.