Ground (<0.15 mm) bentonite was mixed 0-20% with molten sulfur at 140-150degreesC and formed into 5-mm granules that were kept up to 6 weeks in water and stirred 1 min everyday. With 0-6% bentonite granules in 2 weeks, pH of supernatant water fell from 8.8 to 8.1, whereas SO42- and suspended matter rose to 136-157 and 40-363 mg/L, resp. These tendencies augmented as the bentonite content was increased and time protracted to 4 and 6 weeks. Com. tests run in a 55-m high tower used to prill (92:8 w/w) S-bentonite at 140degreesC, gave 2.8, 65.7 and 31.5% of fractions <1, 1-4, and >4 mm in size, resp. The supernate data observed in 2-6 weeks were related to particle size.