Sizing particles with a Coulter counter.

A theorem is presented which permits a determination of the amplitude of the signal generated by the passage of a particle of arbitrary shape through a Coulter counter. The theorem is applied to particles of two shapes, a sphere and a prolate spheroid. For the sphere the signal is directly proportional to the volume of the particle. For the spheroid the result is a complicated function of the shape. Two spheroids of the same volume but different shapes will give different signals.