MEASUREMENT OF THE HARD-SPHERE EQUATION OF STATE USING SCREENED CHARGED POLYSTYRENE COLLOIDS

Using a high-resolution digital x-ray camera we have accurately measur ed the density profiles of several sediments of highly screened polyst yrene colloidal spheres suspended in water. From the integral of the p rofile with height we directly measured the osmotic pressure as a func tion of volume fraction. The results are in excellent agreement with c alculations of the hard-sphere equation of state for both the crystall ine and disordered states. These results demonstrate experimentally th at particles with a hard-sphere force law indeed exhibit the liquid-so lid phase transition at the predicted volume fractions.