VAPOR-LIQUID-EQUILIBRIUM OF WATER TRIOXANE FORMALDEHYDE MIXTURE

Recently, we have developed a new model for describing vapor-liquid equilibrium of the water-formaldehyde and methanol-formaldehyde systems. This model superimposes a physical theory onto the chemical theory for describing liquid-phase behavior of formaldehyde in active solvents. Maurer recently reported vapor-liquid equilibrium data for the water-trioxane-formaldehyde system. The characteristic of this system is the contemporaneous presence of an active (water) and an inert (trioxane) solvent together with formaldehyde. To test our model, we have fitted the experimental data of Maurer using only three adjustable parameters: the zero pressure Henry's constant of formaldehyde in trioxane and, in the expressions for the activity coefficients which account for interactions between water and trioxane and trioxane and formaldehyde, two physical parameters. The results are satisfactory and the thermodynamic model proposed can be used with confidence to describe vapor-liquid equilibrium of formaldehyde in the presence of an active and of an inert solvent.