Two-scale-factor universality near the critical point of fluids

Experimental evidence is presented in support of the validity of the hypothesis of two-scale-factor universality for the correlation function of fluids near the gas-liquid critical point. For Xe, SF₆, and CO₂, the dimensionless quantity $\text{R = ξ}{}_0\text{(}\text{B}{}^2\text{P}{}_{\mathrm{c}}\text{Γk}{}_{\mathrm{B}}\text{T}{}_{\mathrm{c}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$ is universal within the experimental accuracy of 10% and agrees with the value predicted by theory.