Apparent Molar Heat Capacities and Volumes of Mixed Electrolytes: [NaCl(aq) + CaCl2(aq)], [NaCl(aq) + MgCl2(aq)], and [CaCl2(aq) + MgCl2(aq)]

Abstract

Heat capacities and densities of aqueous solutions containing mixtures of simple electrolytes, [NaCl(aq) + CaClz(aq)l, [NaCUaq) + MgCl~(aq)l, and [CaCldaq) + MgCldaq)], have been measured from 298.15 to 373.15 K a t 0.6 MPa. For each system, values were obtained for full ranges of mixture compositions for total ionic strengths of approximately 3 and 5 mol-kg-1. Measurements for NaCl(aq) (0.11-5.95 mol-kg-l), MgClz(aq) (0.44-5.19 mol-kg-l), and CaCldaq) (1.46-5.54 mol-kg-') are also reported. The measurements were done using a flow differential heat capacity calorimeter in series with a vibrating-tube densimeter. Values for the apparent molar heat capacities and volumes are reported and compared to literature values and to values predicted by both Young's rule and Pitzer's theory.

A Low-Temperature Aqueous Thermodynamic Model for the Na–K–Ca–Mg–Cl–SO4 System Incorporating New Experimental Heat Capacities in Na2SO4, K2SO4, and MgSO4 Solutions

“…(2) We force θ and ψ to be less than ±0.1, θ L and ψ L to be less than ±10 –3 , and θ J and ψ J to be less than ±10 –4 . These constraints are based on typical values for these parameters at 298.15 K. ,, (3) We force heat capacities to decrease with decreasing temperature and exclude data points that increase in heat capacity with decreasing temperature. The rationale for forcing heat capacities to decrease with decreasing temperature in our model is discussed in Toner and Catling …”

Thermodynamic Properties of Aqueous Magnesium Chloride Solutions From 250 to 600 K and to 100 MPa

“…These results were chosen primarily on the basis of their coverage of wide ranges of temperature, pressure, or molality. Thus, in addition to the results [11][12][13][30][31][32][33][34][35][36][37][38][39]41,42, used by Holmes et al, 2,3 the following high-temperature and/or high-molality results were included: ͑1͒ Newly published volumetric data of Obsil et al; 18 ͑2͒ vapor pressure data of Lindsay and Liu, 4,5 Urusova and Valyashko, [6][7][8] and Emons et al; 9 ͑3͒ new enthalpy of dilution data of Wang et al 10 and those of Gillespie et al 11 and Simonson et al 12 at temperatures greater than 523 K; and ͑4͒ heat capacity data of White et al 13 for TϾ499 K. Additionally, freezing-point depression data of Rodebush 14 and those from the International Critical Tables of Numerical Data ͑ICT͒ 15 were also included, together with those of Gibbard and Gossmann, 42 to extend the model down to a temperature of approximately 240 K. Additional data that were considered in the data analysis also included vapor pressure results of Sako et al 43 and Derby and Yngve, 16 isopiestic molalities of Kuschel and Seidel, 40 heat capacity results of Saluja et al, 57 and volumetric results of Romankiw and Chou, 65 Saluja et al 57 and Pepinov et al 17 For the correct application of the least-squares method, relative weights were assigned to each set of the experimental results to reflect their different variances. The assignment of the weight was based on the compatibility of one set of results with others, the thermodynamic consistency of the data with other properties, and...…”

Thermal and volumetric properties of complex aqueous electrolyte solutions using the Pitzer formalism – The PhreeSCALE code

“…(5), an additional independent set of parameters is included in the database to account for temperature-variable pressure effects. Many authors have proposed different temperature dependences for these parameters (Krumgalz, 2000;Saluja et al, 1995). We chose the one proposed by Phutela and Pitzer (1986b) which can be formally made compatible with Eq.…”