The problem of efficient washing was first approached with a view to providing excess wash, it being reasoned that as long as excess wash was available the maximum number of displacements through the filter could be attained dependant only on the efficiency of a filter unit. The problem would then be one of effective removal of this excess. B W Wilson's report (1) had already shown that with three displacements and other conditions which were readily reproducible in the Chemical Pilot Plant, and under visualized full scale operating at Port Pirie, washing to within specification was feasible. However, no means of complete removal of excess wash was found and keeping in mind continuous operation on the large plant, a procedure was evolved whereby dilution of slurries was avoided but the chloride and sulphate, in the filter cake and dried product, was maintained within specification.