Measurement of polarization of the tyndall beam of aqueous suspensions as an aid in determining particle size

The relation between particle size and the degree of polarization of the Tyndall beam created by suspension of non-uniform particulate substances was investigated for three materials (silica, granite, and calcite) ranging in size from one to fifty microns. The degree of polarization was found to be a function of the arithmetic mean diameter of the material. The optical property of birefringence was also found to be a determining factor although its effect was not studied quantitatively. It is shown that by combining the equation expressing the relation between particle size and strength of Tyndall beam with the mathematical relation between degree of polarization and particle size, an indirect method of obtaining a complete definition of particle size is given. Particle size values calculated from observed Tyndall readings and measurements of polarization were found to be within approximately ten per cent. of observed values.