In this work, the use of a spinning disk reactor as a unit for a reaction-precipitation process is investigated. An experimental study is reported concerning the precipitation of barium sulfate from aqueous solutions at 25 degreesC on a spinning disk of 0.5 m in diameter. At a rotational speed higher than 900 rpm, spontaneous precipitation took place and crystals similar to0.7 mum in size were produced. At a supersaturation ratio of 2000, the number of generated crystals is comparable with those reported in the literature when a T-mixer is used, but in the case of the spinning disk, a much lower specific dispersed power is required.