This paper reports the improvements of the dialysis apparatus and operations since there are some problems to be improved in the dialysis method which is applied to determine the ionic and molecular weight of dissolved particles. The hook gauge was utilized in order to control the surface level of the dialysing solution and the solvent to be equal with the precision of 0.02 mm to minimize the osmotic and filtration effects. An accurate agitation velocity for both solutions was maintained and so was the same temperature for both solutions with ${pm}0.01^{circ}C$ precision. The dialysis membrane was fixed uniformly and flatly on one end of the dialysis cylinder by using a newly developed ring. The volume change of the dialysing solution during the dialysis was reduced to the range of -1.62 ~ +0.92%. Optimum duration of dialysis was searched from the relation between the osmotic and filtration effect and the pore size of the membrane