Pressure of Kirkwood–Alder transition in monodisperse latex

Monodisperse latex, a colloid system consisting of uniform sized spherical particles of synthetic resin, shows a phase transition phenomenon from ordered state to disordered state. In view of the fact that repulsive interaction prevails in stably dispersed colloid, the transition must be of Kirkwood–Alder transition type. In the present work, the pressure of phase transition has been studied, making use of sedimentation equilibrium, at several electrolyte concentrations of the medium. The magnitude of the transition pressure changed as the electrolyte concentration of the medium varied. The transition pressure expressed in terms of reduced pressure at melting point was 13 to 15 when the electrolyte concentration was around 10−2 mole/liter. These values are very close to computational value 11.6 by Alder, Hoover, and Young, indicating that the particles behave as hard spheres under such condition. At low electrolyte concentrations, the value was larger, about 30 at 10−3 mole/liter and 230 at about 10−6 mole/liter, which are in accord with the result of Hoover et al. for a soft core system.