A theory of colloid stability proposed in the 1940s by the Soviet scientists Boris Derjaguin and Lev Landau and independently by the Dutch scientists Evert Verwey and Theo Overbeek. The DLVO theory takes account of two types of force in a stable colloid: the van der Waals' force, which is attractive and binds particles together, and electrostatic repulsion. The total interaction potential can be calculated as a function of distance, with colloid stability being attained when the two forces balance each other. The DLVO theory is the basis for understanding colloid stability and has a considerable amount of experimental support. However, it is inadequate for the properties of colloids in the aggregated state, which depend on short-range interactions taking into account the specific properties of ions, rather than regarding them as point particles.