The apparent molar heat capacities of dilute aqueous solutions of acetic, propanoic and succinic acid and sodium salts of the two monofunctional acids were measured at 300 K < T < 525 K and p = 28 MPa. Corrections for ionization/ hydrolysis and relaxation effects were applied and the results were extrapolated to infinite dilution to calculate Cop.2. After subtracting the heat capacity of a point mass, the remaining heat capacity was successfully decomposed into functional group contributions at all temperatures. Together with the results of our previous paper on alcohols and dials(2) the heat capacity contributions of the CH2, CW3, OH, COOH, (COOH)2, and COONa groups are now available and these allow reasonably accurate predictions of the heat capacities of all compounds composed of these groups in this temperature range.
