Let r_{1} and r_{2} 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.