Birefringence from Periodic Shear Flow near the Critical Point

The flow birefringence in the binary liquid mixture 2, 6-lutidine and water is measured near its critical point. The effect was produced by periodic variation of the shear, S=∂vₓ∂y, at an angular frequency, ω₀, of 7.5 sec^-1, whereas typical average values of S were 10 sec^-1. Measurements of the temperature dependence of the birefringence phase shift, δ, are in fair agreement with a steady-state theory of Onuki and Kawasaki.