Freezing points in the ternary ZnSO4-H2SO4-H2O system were measured from (0.25 to 2.0) mol kg (1) ZnSO4 and (0.25 to 2.0) mol kg (1) H2SO4. The experimental data was compared with predictions made with a multi-component Pitzer model and Zdanovskii's mixing rule. Good agreement between measured and predicted results was achieved. (C) 2018 Published by Elsevier Ltd.