The specific heat anomaly in triethylamine–heavy water near the critical solution point

Abstract
The anomaly in the specific heat Cpx has been investigated by means of a constant heating rate method. Accurate results could be obtained for ‖TTc‖/Tc values as small as 7×10−6. From a range shrinking procedure and nonlinear‐least‐squares fits to the data we obtained α=α′=0.107±0.002, which is close to the renormalization group (RG) value αRG=0.110±0.008 for the Ising model for the dimensionality d=3. For the universal amplitude ratio A′/A of the diverging part of the specific heat above and below Tc, a value of 1.75±0.03 is obtained. This is also in agreement with theoretical predictions for the Ising model. Combining the amplitude of the correlation length with the critical amplitude of the specific heat allowed us to test two‐scale‐factor universality. For the universal constant X=Avξ30/kB in this system, a value of (1.9±0.4)×10−2 is obtained, which is in agreement with theory and with results for other fluid systems.