PROPERTIES OF ORGANIC-WATER MIXTURES .X. ACTIVITY COEFFICIENTS OF SODIUM CHLORIDE AT SATURATION IN WATER MIXTURES OF POLYGLYCOLS AND POLYGLYCOL ETHERS AT 50 DEGREES

The solubility of NaCl in water mixtures of a number of organic solvents was determined at 50° by packed-column techniques. The solvents included ethylene glycol (EG) and polyethylene glycols (PEG) to molecular weight 1000, monomethyl ethers of EG and PEG to mol wt 750, and dimethyl ethers of EG and PEG to mol wt 1230. From the solubility data, activity coefficient ratios Γ* of NaCl were computed and compared as a function of molecular weight and functional end groups. As expected, the influence of the end groups on Γ* becomes less as the molecular weight increases. A value for Γ* of ca. 20 is predicted at 50° for infinite chains of ethoxy groups (or films) containing 5% water. Implications for hyperfiltration membranes are discussed.