a highly pure cyanuric acid is produced by a process which comprises gradually adding a nitrogenous material capable of producing cyanuric acid , such as urea , to a hot n - methylpyrrolidone solvent . the overall process converts substantially all of the urea to cyanuric acid which , upon drying , is a free flowing product capable of being converted into trichloroisocyanuric acid and similar compounds with a minimum of extra processing while allowing substantially complete recovery of the n - methylpyrrolidone solvent for reuse .