Magnetic birefringence particle size distribution

A novel use for magnetic birefringence experiments is in the measurement of the birefringence of commercially important colloidal vermiculite particles. When aligned in a magnetic field, results at low field strengths show a steady state birefringence proportional to the applied field. The effects on the relaxation time of the birefringence on removal of the field are found to decrease with increasing field strength. This has been attributed to polydisperity of particle size. A theory analogous to that of electric field relaxation and used for magnetic field relaxation data has been further developed and modified to incorporate the more general case of diamagnetism. The modified theory is then used to obtain a two-parameter log-normal size distribution function for the suspended particles. The experimental results obtained are in accord with data acquired from electron micrographs. It is therefore concluded that use of the modified theory is justified and forms the basis of a valid measurement technique applicable to rigid particulate systems of any uniform, regular spheroidal morphology.