Useful remarks to reduce experimental information required to determine water content of gas in equilibrium with gas hydrate, ice or liquid water

Experimental data regarding the water content of gases at low temperatures, especially near and inside the gas hydrate or ice formation regions, are rare and scarce. This is partly due to the fact that the water content is very low under these conditions and, hence, is generally difficult to measure. Furthermore, reaching equilibrium at low temperatures is a time-consuming process. In this communication, we present useful remarks to reduce the amount of experimental information required to determine the water content of a gas in equilibrium with a condensate, gas hydrate, or ice. The need for measuring the water content of a gas phase in equilibrium with a liquid water phase for tuning interaction parameters between water and gaseous component in an equation of statenamely, the Valderrama modification of the Patel−Teja equation of statealong with non-density-dependent mixing rules, is first examined. It is shown that the use of experimental data on the solubility of the gas in the liquid water phase can lead to acceptable estimation of the water solubility in the gas phase. To estimate the water content of a gas in equilibrium with gas hydrate or ice, expressions based on the equality of fugacity in equilibrium phases for relating water content in equilibrium with gas hydrate/ice to corresponding water content in equilibrium with metastable liquid water are then presented. The results are compared with some selected experimental data from the literature showing that the use of data on the corresponding water content in equilibrium with metastable liquid water can lead to relatively acceptable predictions of the water content in equilibrium with the gas hydrate/ice.