Question

At what temperature the surface tension of the liquid vanishes

Answer 1

The rule of thumb is that surface tension decreases with the increase of temperature, reaching a value of zero at the critical temperature. The rule - Eötvös rule,that the rate of change of molar surface energy with temperature is a constant for all liquids - is the named after the Hungarian physicist Loránd Eötvös (1848–1919). This enables the prediction of the surface tension of an arbitrary liquid pure substance at all temperatures. The density, molar mass and the critical temperature of the liquid have to be known.

At the critical point( TEMPERATURE ) the surface tension is always zero.