Capillary constant and surface tension of dimethyl ether and n-butane at temperatures from 214 K to those close to the critical point

The capillary constant a2 has been measured by the differential capillary-rise technique and the surface tension σ of dimethyl ether and n-butane has been determined with the use of data on the densities of saturated liquid and gas. The experiments with dimethyl ether were performed at temperatures from 214 K to 390 K, for n-butane – from 278.15 K to 423.04 K. Equations that approximate the temperature dependences of a2 and σ have been suggested.