Universal amplitude ratios of surface tensions near a critical point in a liquid binary system: Water-2,5 lutidine

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Abstract
Experimental data of surface tensions along the critical isochore (1) and the two branches of the coexistence curve (2,3) for the water‐2,5 lutidine system have been used in order to check signs and values of the universal amplitude ratios of the critical laws in the forms σα,j =σ c +A(T−T c )+B j (T−T c )μ, j=1,2,3, with imposed μ=1.26. A and the B j ’s being highly correlated, several statistical tests using the values of the ratios have been used. Experimental values are compatible with P +=B/B i =−0.59 (B: isochore; B i : interfacial tension in the two phases system), maybe with Q=B/B‘=−0.83 (B‘ one branch of the coexistence curve) and certainly with its sign. The other ratios cannot be verified at all by the experimental data.