Gas solubilities in liquid water near the temperature of the density maximum, T _max(H₂O) = 277.13 K

Abstract: Liquid water has a density maximum at Tmax(H2O) = 277.13 K, and around this temperature the structure of the liquid changes significantly. In order to investigate the impact of such an unusual solvent density behavior upon the temperature dependence of Henry fugacities h2 , 1(T, P) (also known as Henry’s law constants) and related quantities of aqueous solutions of gases, that is, in particular, in order to solve the question of the existence of a point of inflection in curves h2 , 1(T) vs. T near Tmax(H2O), we use results of high-precision gas solubility measurements in water of He, Ne, Ar, N2, and O2, where h2 , 1(T) data have been reported for reasonably large and reasonably fine temperature grids around Tmax(H2O). Focusing on the temperature region 273.15<T/K<285.15, the discussion is essentially based on analysing difference quotient plots Δ(lnh2,1)/Δ(1/T) vs. Tavg. These plots summarize solubility results obtained at adjacent temperatures Ti and Ti + 1, with Tavg=(Ti+Ti+1)/2 being the average temperature, and are closely related to plots of ΔH2∞(Tavg) vs. Tavg, with ΔH2∞ being the partial molar enthalpy change on solution of the gas in water. The question is essentially resolved through including in the discussion insight gained from calorimetrically determined enthalpies of solution, i.e., through use of high-precision results obtained from flow-calorimeters originally designed by Gill and Wadsö in 1982 and 1984, respectively. Careful analysis of experimental results accumulated so far on the temperature dependence of the Henry fugacity around Tmax(H2O) and on corresponding enthalpies of solution do not support any unusual behavior of h2 , 1 in this temperature region. Graphical abstract: [Figure not available: see fulltext.].