Cloud-point measurements of the {H2O + poly(ethylene glycol) + NaNO3} system

The cloud-point (CP) temperatures and phase separation of {H2O + poly(ethylene glycol) + NaNO3} ternary system is studied by the turbidimetry method using a reaction calorimeter. The phase separation was also observed by visual inspection. Differences between the CP measured using the turbidimetry method and visual inspection, was up ±0.5 K. The Flory–Huggins model with a temperature and concentration-dependent interaction parameter was employed to correlate the phase diagram of the system. As a result of the correlation an average absolute deviation of 0.002 is obtained.

► CP temperatures of the {H2O + PEG + NaNO3} system were measured by the turbidimetry method.
► CP temperatures at constant NaNO3 concentration and different concentrations of PEG were measured.
► For a constant NaNO3 concentration, CP temperature decreases as the PEG concentration increases.
► For a constant PEG concentration, CP temperature decreases as the NaNO3 concentration increases.
► The phase diagram was correlated by the Flory−Huggins model.