Critical behavior of {DMA + AOT + n-octane} nonaqueous microemulsion with the molar ratio (ω = 2.66) of DMA to AOT

摘要

To examine the critical behavior of the nonaqueous microemulsion, we have determined the coexistence curves of (T, n), (T, φ) and (T, φ) (n,φ,φ are the refractive index, the volume fraction, and the effective volume, respectively) for a ternary microemulsion system of {N,N- dimethylacetamide (DMA) + sodium di-(2-ethylhexyl) sulfosuccin-nate (AOT) + n-octane} with the molar ratio 2.66 of DMA to AOT by measuring the refractive index at constant pressure within about 7 K from the critical temperature T _c. The critical exponents β and critical amplitudes B have been deduced from (T, n), (T, φ) and (T, φ) coexistence curves; the critical exponents β are in good agreement with 3D-Ising exponent for the ternary system. The experimental results have been analyzed to examine the diameters of the coexistence curves, and to discuss the goodness of density variables for constructing order parameters.