Density fluctuations and specific heat near the critical point

The density dependence of the proton magnetic shielding constants in liquid methanol and ethanol has been accurately measured at a temperature of 29.2°C and at external pressures between 1 and 2500 bar. For comparison, a measurement in the vapor coexisting with the liquid at 29.2°C has also been made. For the carbonyl protons the results appear to be in qualitative agreement with previous measurements of the density dependence of the shielding constants in methane and ethylene. The results are discussed theoretically on basis of the Buckingham electric field model.