Proton spin relaxation in the critical mixture of nitrobenzene and hexane

Abstract

The proton spin-lattice relaxation time (T 1) has been measured separately for the protons in the nitrobenzene molecules and in the hexane molecules in a critical mixture over a range of temperatures including the critical mixing temperature (17°c). T 1 has also been measured for pure liquid nitrobenzene and for pure hexane in the same temperature range. Well above the critical mixing temperature the solution T 1 values are as expected. They become anomalous some 20°c above the critical mixing temperature in contrast with the shear viscosity, which only becomes anomalous a few degrees above. The two anomalies are inconsistent. The separation into two solutions is undetected by proton spin relaxation. The T 1 of the hexane rich solution in the immiscible region is also anomalous.