Dynamics of concentration fluctuations for butylcellosolve in water

The coexistence curve, the shear viscosity, and the angular and the spectral distribution of scattered light have been measured for butylcellosolve in water near its lower critical mixing point. We have examined the validity of the pseudospinodal concept for the interpretation of the diffusion coefficient near the critical point. The critical exponents obtained with the assumption of the pseudospinodal agree with the recent experimental and the theoretical values. The universal dynamic amplitude ratio R=1.03±0.06 obtained in the present work is in disagreement with the value R=1.2 calculated from the renormalization-group theory but in good agreement with R=1.03 of the prediction by Burstyn et al. The diffusion coefficient as a function of temperature and concentration is well represented in terms of a scaled function.