UNIVERSAL AMPLITUDE RATIOS OF SURFACE TENSIONS NEAR A CRITICAL-POINT IN A LIQUID BINARY-SYSTEM - WATER-2,5 LUTIDINE

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 cheek signs and values of the universal amplitude ratios of the critical laws in the forms sigma(alpha,j)=sigma(c)+A(T-T-c)+B-j(T-T-c)(mu), j=1,2,3, with imposed mu=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.