Abstract: Suspension or solutions of cyanuric chloride in water are prepared at high mixing velocities and low temperatures with resulting low degree of hydrolysis by introducing liquid cyanuric chloride through a nozzle in the upper portion of the mixing apparatus in countercurrent flow to upwardly flowing water introduced from at least one lower nozzle above a breast shaped constriction in the lower, open portion of the apparatus. In this way the chamber walls are always covered with an unbroken layer of liquid. The process can be carried out at normal, reduced or elevated pressure. At reduced pressure by evaporation of the water there is simultaneously a cooling of the system.