Synopsis An equation is suggested for the variation of dielectric constant of mixture of polar liquids with concentration c and temperature T (°K): e = ( l + m / T ) + ( p + q / T 1/2) c + Z c 2 where l, m, p, q , and Z are constants. When variation of ɛ with c is linear, only first two terms are sufficient. The equation has been illustrated for Water-Methyl Alcohol and Water-tert.-Butyl Alcohol mixtures with satisfactory results.