H-1 AND H-2 NMR-STUDIES OF MIXTURES 2,6-LUTIDINE WATER NEAR THE LOWER CRITICAL SOLUTION POINT

Deuteron spin-lattice relaxation time (T1) measurements of binary mixtures 2,6-lutidine/D2O have been done near the lower critical solution point (T(C, L), epsilon = (T-T(C,L))/T(C, L) greater-than-or-equal-to 10(-5). Singularities are observed at T(C, L). The changes in the slope of T1 (H-2) = f(T) can be interpreted as due to the effect of concentration changes on T1 and simultaneously strong overlaping of H-2 NMR signals from coexisting phases. In the two-phase region, ca. 2-degrees-C above T(C, L), two D2O signals with very strong temperature evolution have been detected. Similar doubling of 2,6-lutidine H-1 NMR signals has been observed already at T-T(C, L) less-than-or-equal-to 1-degrees-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 D2O signals-delta'-delta" possess the property of an order parameter, i.e. delta'-delta" approximately epsilon(beta) with beta = 0.336 +/- 0.030.