Measurement of the deposit formed by a particulate suspension on a membrane

A technique of differential profilometry is reported which allows direct me asurement of the deposits formed on a membrane. The technique is described and demonstrated to be capable of resolving deposits of one mum or less. Si multaneous measurements of the flux collected in a segmented manner along t he operating membrane allow the calculation of the resistivity of the depos it formed. Microfiltration experiments at different velocities result in th inner deposits at higher velocities and higher fluxes. The deposits initiat e downstream of the entrance, build somewhat erratically, then inexplicably diminish near the downstream end of the membrane. The method may lead to o ptical methods capable of continuous observations during operation.