Process for making crystals

A process for preparing crystalline particles of at least one active principal in the presence of ultrasonic irradiation, the process comprising contacting, in a closed flow loop comprising an ultrasonic flow cell chamber, a solution of at least one solute in a solvent in a first flowing stream with an anti-solvent in a second flowing stream, causing the mixing thereof, wherein the flow rate ratio of the anti-solvent:

• solvent is higher than 20:1, the mixture in the ultrasonic flow cell chamber being subjected to ultrasonic irradiation, the ultrasonic irradiation inducing nucleation and subsequent crystallisation of the at least one solute, recirculating the second flowing stream around the closed flow loop and collecting the crystalline particles that are generated.