In this method the liquid of which the latent heat is to be determined is contained in a glass vessel which is suspended by a fine wire from the hook of a balance, and the amount of electrical energy is measured which is required for the evaporation of an observed mass. The electrical energy is supplied by a large current passing through a small resistance in the liquid itself. In order to reduce heat losses as much as possible, the vessel carrying the liquid and the resistance is completely surrounded by a doublewalled shield, which is filled by the saturated vapour of the liquid itself. The estimation of the electrical energy supplied necessitates tne measurement of the current, C (amperes), the resistance R (ohms), of the heating coil, and the time in seconds, T, during which the current flows. It is expressed by C2RT joules, and if M be the mass evaporated in gms., the latent heat expressed in joules per gm. becomes C2RT/M.