Investigations on the passage of light through suspensions

AbstractAn examination has been made of the manner in which light passing through suspensions of solid materials in water, and the light scattered from such illuminated suspensions, depends upon the particle size of the suspension. The following conceptions are introduced: the specific extinction coefficient of a suspension (ē) and the specific nephelo‐value of a suspension (v̄)The examination has been made in order to find out how these two quantities vary with the grain size of white as well as of some coloured suspensions. For white suspensions, monodisperse preparations of barium sulphate produced by condensation and fractions of ground barytes produced by elutriation are used; for coloured suspensions, elutriated fractions of chromic oxide and of pyrolusite are used. Special care has been devoted to the production or suspensions with a very high grade of monodispersity.It is found that ē as well as v̄ for the white suspensions have a distinct maximum at grain sizes of the same order as the wavelength of the transmitted light, whereas ē by the coloured suspensions shows a maximum at grain sizes which are several times smaller than the corresponding grain sizes in the white suspensions.