1965 Kaasenbrood Stamicarbon 3184508 crystallisation
This first patent of Petrus Kaasenbrood, later the inventor of the CO2 stripper, describes the production of low biuret urea by means of crystallisation.
Kaasen brood suggest to crystallize at somewhat higher temperatures in order that normal cooling water can be used. At these higher temperature a double salt 2urea.1biuret is formed. After adding water the urea will dissolve again.