Published and additional data for polyethylene glycol 8000 (PEG), formerly PEG 6000, solution water potentials (Psi) are compared. Actual bars Psi over the concentration range of 0 to 0.8 gram PEG per gram H(2)O and temperature (T) range of 5 to 40 degrees C are best predicted (probably within +/- 5%) by this equation: Psi = 1.29[PEG](2)T - 140[PEG](2) - 4.0[PEG]. Although transformable through division by [PEG] to virial equation form, results indicate that the coefficients are not virial. Mannitol (MAN) interacts with PEG to produce Psi significantly lower than additive. Vapor pressure osmometer (VPO) data for MAN-PEG synergism compared favorably with those from thermocouple hygrometry; and VPO data showing the interactions between PEG and four salts are presented. The synergism of MAN-PEG and of NaCl-PEG are related linearly to the concentration of solute added with PEG.
