Thermodynamics of proton dissociations from aqueous l-valine and l-2-amino-n-butanoic acid: apparent molar volumes and apparent molar heat capacities of the protonated cationic, neutral zwitterionic, and deprotonated anionic species at temperatures from 278.15⩽T/K⩽393.15, at molalities 0.015⩽m/mol·kg−1⩽0.67, and pressure p=0.35 MPa