Content Handbook F

Outline of method

A modified Andreason method is described in which a uniformly dispersed suspension of the DDT in standard water settles under stable conditions. Samples are withdrawn from a fixed point in the suspension, after given times, and the DDT content of each is then determined.
It is assumed that the suspension is sufficiently dilute to allow settling without mutual particle interference and, also, that Stokes' Law is obeyed.

Scope

This method can be used for the evaluation of sedimentation of DDT and its carriers in wettable powders.
The method gives the total number of particles, less than 50, 20 and 10 ìm (particle size distribution), expressed as percentage by weight of DDT.