Second virial cross coefficients for (ammonia + water) derived from gas phase excess enthalpy measurements

The heat of mixing and second virial cross coefficient of water+oxygen and water+nitrogen

“…The flow calorimetric apparatus used to make H E m measurements on (water + nitrogen) and (water + oxygen) is almost the same as that previously described [4,5]. The plug-in calorimeter was a single vessel, not a twin arrangement.…”

“…A graph showing B ns and B for water over the temperature range (300 to 550) K is shown in figure 3 of reference [5] (curves 5 and 1). In terms of the association model the difference between these two curves is the quantity RT Á K. Values of ln K 1 at T 1 and ln K 2 at T 2 plotted against T À1 at once give the enthalpy of association DH.…”

“…A further development was the construction of a plug-in gas phase flow mixing calorimeter [4] which could be easily removed and modified as required. This calorimeter has proved to be invaluable for measurements on polar fluid mixtures [5] and is the one used for the measurements reported here.…”

Ammonia–benzene association. Second virial cross coefficients for ammonia–benzene and ammonia–cyclohexane derived from gas phase excess enthalpy measurements

“…The gas phase flow calorimetric apparatus was the same as that described previously (3) and used to make measurements on (steam + ammonia). Again a 'plug in' flow mixing calorimeter (4) was used.…”

“…Curve c drawn through the measurements was calculated from Stockmayer potential parameters for ammonia and Kihara potential parameters for cyclohexane using (1 − k 12 ) = 0.92, which best fits both the H E m (B) and therfore the B 12 values. The uncertainty on the values of B 12 is estimated to be ±15 cm 3 ·mol −1 , and the uncertainty on the values of φ 12 is estimated to be Figure 2 also shows the second virial coefficients for ammonia (curve a), benzene (curve e) and cyclohexane (curve f). The B 12 curve for ammonia-cyclohexane (curve c) is only about 30 cm 3 · mol −1 more negative than the curve for ammonia (curve a) because dipole-induced dipole forces between ammonia and cyclohexane are very weak.…”