Abstract: A dissolving device for dissolving a particulate solid in a supercritical or almost critical fluid comprises a circulation loop, in which there is a feed for feeding a feed stream of the supercritical or almost critical fluid, a cyclone, which is in communication with the feed and has a principal discharge for discharging a principal discharge stream of a solution of the particulate solid in the supercritical or almost critical fluid and has an auxiliary discharge for discharging an auxiliary stream of the supercritical or almost critical fluid with solid particles dispersed therein, the auxiliary discharge being in communication with the said feed. A dissolving device of this type has a low pressure drop and a high dissolving rate compared to the prior art.