An investigation of the volumetric properties of l -alanine and sodium bromide in water at elevated temperatures and pressures

The partial molar heat capacities of glycine and glycylglycine in aqueous solution at elevated temperatures and atp= 10.0 MPa

“…Several authors have previously utilized the HKF equations to model the volumetric and thermochemical properties of aqueous amino systems at infinite dilution. (1,7,21) Experimental results for heat capacities reported in this study and the recent work of Clarke et al, (22) in addition to recent high temperature and pressure volumetric measurements on aqueous amino acid systems, (2,3,14,32) have indicated that HKF model predictions published by Amend and Helgeson (1) and others (21) are in error. One of the intentions of this study is to utilize recently determined partial molar volume data at elevated temperatures and pressures (3,14,32) and the partial molar heat capacity values reported in this paper to derive an improved set of coefficients to the HKF equation for aqueous glycine solutions; a set of coefficients that may be used to model experimental data precisely.…”

“…The results from these studies (2,3,14) indicate that the partial molar volumes of the amino acids at high temperatures and pressures are in poor agreement with those predicted using the modified HKF semi-empirical equations of state. (19) Whereas the experimental partial molar heat capacities at infinite dilution reported in this study approach increasingly negative values with increasing temperature, those values obtained using the Amend and Helgeson (1) coefficients to the HKF equation become increasingly positive with increasing temperature.…”

“…(44) The quantity V z does depend on pressure, but only to a small extent. Assuming that the change in isothermal compressibility for reaction (7) is the same as that estimated (45) for the change in isentropic compressibility, then the value of V z at p = 10.0 MPa is −15.8 cm 3 · mol −1 . As the difference (0.3 cm 3 · mol −1 ) is within the uncertainty associated with the estimation of the quantity V z , (44) a value of −16.1 cm 3 · mol −1 has been used in our calculations.…”

“…(55) Hakin and co-workers (3,32) have recently reported models for the partial molar volumes of glycine and glycylglycine in water that were derived from the revised HKF semiempirical equations of state. Input data sets to these models were obtained from an experimental investigation of the temperature and pressure surfaces of the densities of aqueous solutions of glycine and glycylglycine.…”

“…Clarke and Tremaine (2) have reported the volumetric properties of several amino acids in aqueous solution at elevated temperatures and pressures. Similarly, Hakin and coworkers (3,14) have determined the partial molar volumes of glycine and L-alanine over the range 398…”