The apparent integral diffusion coefficients of ceric sulphate solutions, 4 normal in sulphuric acid, were measured for concentrations ranging from 0.05 normal to 0.415 normal at 25°C with the use of a pyrex sintered glass diaphragm diffusion cell. A graph obtained by plotting the calculated integral diffusion coefficients versus the square root of the initial concentration is similar to the graphs obtained for uni-univalent salts. The rate of diffusion, however, is less by a factor of ten. The sintered glass diaphragm cell was calibrated with 0.1 normal potassium chloride at 25°C and the value of the cell constant was determined to be 0.1111 ± 0.0002 cm⁻².