By Ostwald-Walker dynamic method, the relative lowering of vapour pressure, lowering of vapour pressure and vapour pressure of the solvent, all can be measured. In this method, the apparatus used, contains two bulbs: bulb A contains solution and bulb B contains solvent. The loss of weight in bulb B gives the lowering of vapour pressure and total loss of weight in both the tubes gives the vapour pressure of the solvent and Relative lowering of vapour pressure =vapourpressureofsolventloweringofvapourpressure