A study has been made of the electrolysis of aqueous MgSO4.7H2O in the presence of varying proportions of H2SO4. The influence on the production of persulphate of the following factors has been investigated composition of the electrolyte, inter-electrode distance, current density at the. anode and the cathode, temperature, duration of electrolysis, addition agents and cathode material. Data are also given for the optimum conditions for the production of the persalt. High yields of persulphate under studied conditions are attributed to the absence of Caro's acid. The probable mechanism of the formation of magnesium persulphate is also indicated.