The Heat Capacities, Entropies, and Heats of Solution of Anhydrous Sod um Sulfate and of Sodium Sulfate Decahydrate. The Application of the Third Law of Thermodynamics to Hydrated Crystals

Abstract

Vol. 00 gen double bond and a single bond, then each bond would possess 50% double bond character. The interatomic distance found by application of the usual resonance curve is 1.69 Á. The discrepancy between this value and that observed is probably due to the importance of electronic structures in which the oxygen is bonded to the selenium atom by a triple bond. A bond of this type is possible because selenium is not restricted rigorously by the octet rule.The observed sulfur-oxygen distance in sulfur dioxide bears about the same relation to the radii as that found for selenium dioxide, and the two molecules are probably closely similar in electronic structure.The selenium dioxide crystal4 does not contain (4) James D. McCullough, This Journal, 69, 789 (1937).discrete SeOs molecules, but instead consists of infinite chains. The observed Se-0 distances in the crystal, 1.78 Á. and 1.73 Á., have been discussed by McCullough.We are indebted to Dr. James D. McCullough for furnishing us with the sample of selenium dioxide, and to Professor Linus Pauling for his aid and criticism during the course of this investigation. SummaryElectron diffraction photographs of selenium dioxide vapor have been interpreted to lead to the value 1.61 * 0.03 Á. for the Se-0 distance. The value of the angle O-Se-O could not be de crmined.Pasadena, Calif.

Acquisition and evaluation of thermodynamic data for mirabilite-thenardite equilibria at 0.1 MPa

“…Although the △G r° and △H r° values obtained in this study were precise, the value for △S r° involves large uncertainties because it was calculated from the difference of two large numbers for △G r° and △H r°. Data from the present study are in excellent agreement with most of the previous vapor-pressure measurements [16,25,28,30,31,35], as shown in Table 4 and Figs. 2 and 3.…”

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

“…We derive the enthalpy of reaction of meridianiite in this study. All other reaction enthalpies, if available, are from the compilation of Wagman et al c The sources of heat capacity data is as follows: thenardite, mirabilite, arcanite, kieserite, epsomite, anhydrite, gypsum, and ice . All other heat capacities were calculated in this study as discussed in section . …”

“… c The sources of heat capacity data is as follows: thenardite, mirabilite, arcanite, kieserite, epsomite, anhydrite, gypsum, and ice . All other heat capacities were calculated in this study as discussed in section . …”

High temperature properties and decomposition of inorganic salts :

“…The nomenclature for the crystal forms is that of Kracek [66]. The value for the heat of formation of Na 2 S 04 , -330.90 kcal mol -1 , in [1] was calculated there from data of Pitzer and Coulter [113] who used Na 2 S04(V). According to Coughlin [26] there is a constant A// = 0. , while [106] shows a TGA curve level only to 573°K, then falling off gradually for a total weight loss of 1 percent by 1157°K.…”