Isopiestic Determination of the Water Activities of Poly(ethylene glycol) + Salt + Water Systems at 25 °C

Water activities of poly(ethylene glycol) (PEG) + salt + H 2 O systems have been measured using an improved isopiestic method at 25 °C. The salts used were MgSO 4, (NH 4 ) 2 SO 4, KH 2 PO 4, and K 2 HPO 4 . The water activities were correlated successfully with an empirical equation.