The Viscosity Anomaly Near the Lower Critical Consolute Point

Shear viscosity measurements for a critical mixture of 3-methylpyridine + heavy water near a lower critical consolute point are reported. The background contribution was determined from viscosity measurements of mixture at a noncritical composition. In the entire investigated temperature range Tc— T^ 15.6 K, the viscosity of the critical mixture exceeds the background contribution, and the critical enhancement is important. The increase of the viscosity near critical is found in the temperature range 7"c—7s; 1.82 K. The critical exponent r = 0.0415 ±0.002 and the wave number Q = (0.40 + 0.07) nm"1 are determined.