The solids in Purex lww were first observed during flowsheet tests for recovery of fission products from plant wastes. Since the nature of this solid was not apparent from the flowsheet composition of lww, some work was performed to characterize this material. Although this work has been conducted over a period of about one year, it has been subordinate to the main one of testing flowsheets for fission product recovery. The solids have been observed in each of about six samples of plant lww that have been studied, and the centrifuged volume of solids has been about four percent in each case.