Let r1 and r2 be the radii of the lower and the upper ends of the capillary. The radius r at height h at the position of the meniscus is given by
Surface tension of the liquid at 0ºC
If r´ is the radius of the cylindrical tube B, then at 0º C
and at 50ºC
Rate of change of surface tension with temperature, assumed constant for S (θ) as a linear function, will be
Thus, the surface tension decreases at the rate of 1.4 × 10–4 N/m per degree celsiusrise in temperature.