1. Alexander, A. E., and Johnson, P., “Colloid Science”, 603 (Clarendon Press, Oxford, 1949).
2. Liesegang, R., Z. phys. Chem., 23, 365 (1897).
3. Packter, A., and Matalon, R., J. Coll. Sci. (in the press).
4. Jablczynski, K., Bull. Soc. Chim. Fr., (4), 33, 592 (1923).
5. Wagner, C., J. Coll. Sci., 5 (1), 85 (1950).