J. Peter Hershey

The ionization of boric acid in NaCl, NaCaCl and NaMgCl solutions at 25°C

Abstract The stoichiometric pK ★ for the ionization of boric acid has been determined from emf measurements in pure NaCl solution and in NaCl solution with small amounts of added CaCl2 and MgCl2 from I = 0.5 to 6.0 molal at 25°C. Our results in NaCl media at low concentrations are in good agreement (±0.01 pK units) with the results of Owen and King (1943). From the values of the pK★ we have determined the Pitzer parameters β 0 , β 1 and Co for the interactions of Ca2+ and Mg2+ with B(OH)4−. Ion pairing constants for the interaction of borate ion with Ca2+ and Mg2+ were also determined from I = 0.5 to 6 m and values were extrapolated to pure water. These interactions are weak and the pK s in water and in NaCl solution are in reasonable agreement with values of other workers. Pitzer terms (β[MA]Cl0) for the interaction of [MA] ion pairs with Cl− were also determined. The pK HA ★ data can be fitted within experimental error with one less parameter using the combined ion pairing/Pitzer approach than when using the Pitzer formalism alone. We, thus, favor the combined approach for calculating the ionic interactions in these solutions.

PVT properties of concentrated aqueous electrolytes: V. Densities and apparent molal volumes of the four major sea salts from dilute solution to saturation and from 0 to 100°C

AbstractThe densities of the major sea salts (NaCl, Na2SO4, MgCl2, and MgSO4) have been measured from 25 to 95°C and to saturation. These results have been combined with literature data and fitted to equations of the form

The pK∗ of TRISH+ in Na-K-Mg-Ca-Cl-SO4 brines—pH scales

\Delta d = Am{\text{ }} + {\text{ }}Bm^{3/2} {\text{ }} + {\text{ }}Cm^2 {\text{ }} + {\text{ }}Dm^{5/2}

The PVT properties of concentrated aqueous electrolytes IX. The volume properties of KCl and K2SO4 and their mixtures with NaCl and Na2SO4 as a function of temperature

where Δd=d−do (do is the density of water) and A, B, and C, etc., are polynomial functions of temperature. The standard deviations of the fits were better than ±50×10−6 g-cm−3 for all the salts from 0 to 95°C and to saturation. The apparent molal volumes Vϕ of the salts have been fitted to the equations of Pitzer. The infinite dilution values of Vϕ were in good agreement with literature data, provided the results were not overfit. The large deviations of Vϕ for MgSO4 from additivity as a function of concentration were attributed to the formation of MgSO4 ion pairs.

The dissociation of phosphoric acid in NaCl and NaMgCl solutions at 25°C

The sound velocities of aqueous NaCl, Na2SO4, MgCl2, and MgSO4 solutions were measured from 25 to 95°C in 10o intervals from dilute to saturated solutions. The results were combined with our earlier data and fitted to functions of molality and temperature to within ±0.4 m-sec−1. The adiabatic compressibilities βS were calculated from sound speeds and used to calculate the adiabatic apparent molal compressibilities ξφ. Isothermal compressibilities β and isothermal apparent molal compressibilities χφ were calculated from βS using literature values for the expansibilities and heat capacities. The values of χφ were extrapolated to infinite dilution using the Debye-Huckel limiting law to determine partial molal compressibilities. The apparent molal compressibilities were fitted to Pitzers equations. The Pitzer parameters for the concentration dependence of χφ were determined as a function of temperature. Correlations of χφ and Vφ at various temperatures were found for the electrolytes.

Densities and compressibilities of aqueous sodium carbonate and bicarbonate from 0 to 45°C

Abstract The stoichiometric dissociation constant, pK∗ of TRISH+ has been determined in NaCl, KCl, MgCl2 and CaCl2 solutions to an ionic strength of 6 molal. The results have been used to derive Pitzer coefficients for the interactions of TRIS with Na+, K+, Mg2+ and Ca2+ ions. These results can be used to determine the pK∗ of TRISH+ in mixed brines which can be used to calibrate pH electrodes. Measurements of pK∗ of TRISH+ in mixtures of NaCl-MgCl2, NaCl-CaCl2, NaCl-Na2SO4, KCl-MgCl2 and KCl-CaCl2, artificial seawater and Dead Sea waters were made to determine the reliability of the Pitzer coefficients. The estimated values were found to be in good agreement with the measured values provided corrections were made for the interactions of H+ with SO2−4. It now is possible to use dilute solutions of TRIS and TRISH+ to make buffers that can be used to make reproducible pH measurements in brines.

The partial molal volume of silicic acid in 0.725 M NaCl at 1°C determined by the neutralization of Na2SiO3

Abstract The stoichiometric pK 1 ∗ for the dissociation of H2S has been determined from emf measurements in NaCl from 0.1 m to saturation at 5, 25 and 45°C and in KCl solutions at 5 and 25°C. The values of pK 1 ∗ were also measured in NaCl with small amounts of added MgCl2 and CaCl2 to I = 6.0 m at 25 °C. The results were used to determine Pitzer coefficients for the interactions of HS− ions with Na+, K+, Mg2+ and Ca2+. Values of the pK 1 ∗ , estimated using these coefficients, were found to be in excellent agreement with the measured values. Estimates of pK 1 ∗ in seawater and Dead Sea water calculated from the Pitzer coefficients were in excellent agreement with measured values from 5 to 25°C. Thus, it is possible to characterize the thermodynamics of the first dissociation of H2S in most natural waters from 0 to 50°C and I = 0 to 6 m.

Oxidation of H2S with H2O2 in natural waters

AbstractThe densities of KCl and K2SO4 were measured from dilute solutions to saturation from 5 to 95°C. The data were combined with literature data to produce density and apparent molal volume, Vφ, equations from 0 to 100°C and to saturation. The standard deviations of the density equations were 30×10−6 g-cm−3 and 32×10−6 g-cm−3, respectively, for KCl and K2SO4. Pitzer equations were used to fit the Vφ data. The resulting infinite dilute partial molal volumes, Vo, were in reasonable agreement with literature data. The densities of the mixtures of the six combinations of the salts KCL, K2SO4 NaCl and Na2SO4 were measured at I=2.0 and t=5, 25, 55 and 95°C. The resulting volumes of mixing were fitted to equations of the form