The effect of several chosen admixtures (Al3+, Cu2+, Fe2+, Mg2+, Mn2+, Naand urea) on crystallization of ammonium sulphate was studied. These admixt
ures rise the metastable zone width change the nucleation order, affect the
overall growth rate as well as the growth rate of individual faces and in
this way they change the crystal shape of ammonium sulphate. An explanation
of these effects is suggested.