STATIC AND DYNAMIC LIGHT-SCATTERING EXPERIMENTS WITH A BINARY-LIQUID MIXTURE WITH A MISCIBILITY GAP - STUDY OF THE SYSTEM DIETHYLENE GLYCOLDIETHYLETHER WATER/

Static and dynamic light scattering experiments are carried out with m ixtures of critical and noncritical composition of the system diethyle ne glycol diethylether (abbreviated (C(2)E(1))(2)O/water in the vicini ty of the lower critical point of the system (critical composition, y( c) = 0.6971, y, mass fraction of (C(2)E(1))(2)O; critical temperature T-c = 26.08 degrees C). The system specific values of two critical amp litudes of a mixture of critical composition are determined: the criti cal amplitude of the correlation length xi(o)(+) of local concentratio n fluctuations (xi(o)(+) = (0.283 +/- 0.003) nm; xi(+) = xi(o)(+) epsi lon(-nu); epsilon = (T-c - T)/T-c); nu = 0.630) and the critical ampli tude D-fo(o) of the mutual diffusion coefficient (D-o(o) = 2.88 . 10(- 6) cm(2) . s(-1); D = D-o(o) epsilon(nu); nu* = 0.671). The value of epsilon(o)(+) is combined with the known value critical amplitude sigm a(o) of the liquid/liquid interfacial tension (sigma(o) = 20.4 mN . m( -1)) to calculate the value of the amplitude ratio R(sigma,xi)(+)(= si gma(o)(xi(o)(+))(2)/k(B)T(c)) = (0.387 +/- 0.008) (theoretical value: R(sigma,xi)(+) = (0.35 +/- 0.02)). The pseudospinodal concept (xi = <( xi)over tilde>(o) epsilon(ps)-(<(nu)over tilde>); D = (D) over tilde(o )(o) epsilon(ps)(<(nu)over tilde>) epsilon = (T-ps -T)/T-ps) is used to describe the temperature dependence of xi and D of mixtures of nonc ritical composition (-0.027 <\y-y(c)\<0.051); concentration dependent and system specific parameters: <(xi)over tilde>(o),<(nu)over tilde>, T-ps and (D) over tilde(o)(o), <(nu)over tilde>, T-ps.