Electrical resistance of the system isobutyric acid-water near the critical point

The electrical resistance of sealed solutions of isobutyric acid-water at the critical composition were measured in the reduced temperature range (ε = T/Tc − 1)3.3 × 10−7 ≤ ε ≤ 6.6 × 10−2 using a Jones ac bridge and lock-in amplifier. Temperatures were controlled and measured to ± 0.0001°C. The temperature derivative of the resistance exhibits a strong divergence very close to Tc so that dR/dT [inverted lazy s] ε−d, where 0.56 ≤ d ≤ 0.77 depending on which of the several methods of data analysis presented are used. A mechanism is proposed which relates this strong divergence to the weak anomaly in the shear viscosity near Tc.