Vapour-liquid equilibrium data(VLE) were measured in a Otsuki-Williams still at 9.866×104Pa.Analyses were made for the Ternary system HCOOH-CH3COOH-H2O and the quaternary system HCOOH-CH3COOH-H2O-NaAc in VLE(1mol/(kg solv. ))of NnAc was used. The results show that the favorable effect of NaAc is reflected not only in the chemical action
but also in the physicochemical aspect. This apparently is related to the phenomena of salting out