Guanidyne carbonate was sepd. from mother liquor of melamine prodn. and purified by ion exchange method to remove Fe ions both in lab. under 2-stage static and dynamic conditions and in industrial scale reactor. Com. ion exchange resins were successfully used. The products contained less than 10 ppm Fe. The resins were efficiently regenerated with soins. of EDTA (concn. 25%) and NH(4)NO(3) (concn. 2 mole/L) used as complexants.