Studies in the viscosity of colloids. I. The anomalous viscosity of dilute suspensions of rigid anisometric particles

Abstract

Abstract The laminar flow of a Newtonian liquid is a process the nature of which is so far obscure, but which is characterized by the fact that its maintenance requires the expenditure of energy at a rate proportional to the volume of the liquid and to the square of the velocity gradient maintained in it. The constant of proportionality varies from one liquid to another, and is called the coefficient of viscosity. This definition of viscosity is equivalent to the more common one in terms of tangential force per unit area and velocity gradient. But it is wider in application, and particularly convenient for our purpose, for it enables allowance to be made for the extra expenditure of energy which is involved when particles are suspended in the liquid. By adding this new quantity to the rate of expenditure proper to the flow of the solvent alone, it is possible to arrive at the rate at which energy must be expended in maintaining the flow of the whole system, and so at what may be called an overall viscosity coefficient. It will be seen that the specific viscosity represents just this extra expenditure of energy which results from the presence of the suspended particles.