Coefficients, D-2/1 (Henderson, Kracek, Chlopin) of cocrystallization of low amounts of M2+ ions (m(2+) = {Ni2+, Cu2+, Co2+, Mg2+, Mn2+, Cd2+}) with ZnSeO4 center dot 5H(2)O at 40 degrees C and ZnSeO4 center dot H2O at 50 degrees C have been determined. Their values are very diverse, ranging from 0.12 (for Cu2+ at 50 degrees C) to 1.87 (for Co2+ at 50 degrees C) and generally differ significantly from those obtained at 25 degrees C. Apart from the change of the solubility ratio of cocrystallizing selenates (m(01)/m(02)) they are very strongly affected by crystal structure of selenate hydrates forming at the investigated temperatures. The dependence of the coefficients D-2/1, obtained at 40 degrees C on the radii of M2+ ions permits to derive an empirical formula for their estimation. The results obtained show that it is possible to remove most of the investigated M2+ ions by the crystallization of zinc selenate at various temperatures in order to achieve its purification. (C) 2011 Elsevier B.V. All rights reserved.