*H and H NMR Studies of Mixtures 2,6-Lutidine/Water Near the Lower Critical Solution Point

Deuteron spin-lattice relaxation time (TJ measurements of binary mixtures 2,6-lut idine/D20 have been done near the lower critical solution point (Tc L), e = (T — Tg L)/Tc 10~. Singularities are observed at Tc L . The changes in the slope of Ti (H) = / ( T ) can be interpreted as due to the effect of concentration changes on Ty and simultaneously strong overlaping of H N M R signals from coexisting phases. In the two-phase region, ca. 2°C above Tc L two D 2 0 signals with very strong temperature evolution have been detected. Similar doubling of 2,6-lutidine 'H N M R signals has been observed already at T — Tc L ^ 1 °C. It is shown that the two signals arise from the nuclei in two coexisting phases; they are not due to pecularities of hydrogen bond. The difference between chemical shifts of both D 2 0 signals ö' — ö" possess the property of an order parameter, i.e. ö' — (5"~ e with 0 = 0.336 ±0.030.