The surface tension of a liquid decreases with a rise in temperature except the molten cadmium and copper. For small range of temperatures, the variation of surface tension is given by the formula $S _{ t }= S _{0}(1- at )$, where $S _{0}$ and $S _{ t }$ are the surface tensions of liquid at $0^{\circ} C$ and $t^{\circ} C$ respectively and $a$ is the coefficient of surface tension withtemperature.