  Fluctuations in fluid velocity and fluctuations in electric fields may both
give rise to forces acting on small particles in colloidal suspensions. Such
forces in part determine the thermodynamic stability of the colloid. At the
classical statistical thermodynamic level, the fluid velocity and electric
field contributions to the forces are comparable in magnitude. When quantum
fluctuation effects are taken into account, the electric fluctuation induced
van der Waals forces dominate those induced by purely fluid mechanical motions.
The physical principles are applied in detail for the case of colloidal
particle attraction to the walls of the suspension container and more briefly
for the case of forces between colloidal particles.
