Processes for micromixing of liq. streams with chem. reactions by continuous collision were briefly reviewed. A new apparatus based on 2 perpendicular jets was developed and used for the pptn. of dyes produced by coupling p-N(2)C(6)H(4)SO(3)H with 1-naphthol (test method). The process was recommended for pptn. of pharmaceutical products from reaction mixts. as fine crystals (1-5 mu m).