Iron (II) sulphate, a side product of the steel industry, can react with nitric acid in the presence or absence of sulphuric acid to give a solution of iron (III) sulphate and nitrate. This solution seems to be a good substitute for iron (III) chlorosulphate as a coagulant in water treatment processes. In the present work, a kinetic study of the different reactions taking place has been realised. Experimental measurements of the conversion of Fe(II) to Fe(III) have been carried out by means of a volumetric method. The influence of various operating parameters such as the reaction temperature and the concentration of reagents has been studied. Global kinetic data such as the reaction orders, the reaction rates and the activation energy have been determined. Measurements of the water turbidity and the concentrations of undesirable products such as nitrates, have been taken prior to and after the treatment process and are also reported.