Deuterium isotope effects on the miscibility of nitromethane and water

The miscibility of nitromethane and water and the influence of deuterium substitution over a broad concentration range are reported. The results enable the construction of the phase diagrams for all systems. It appeared that deuteration in the OH group of water increases the region of limited miscibility, while deuteration in the methyl group of nitromethane decreases this region. The isotope shift of the upper critical solution temperature ranges from 1.05 K for deuterated water to −0.16 K for the deuterated nitromethane+regular water system. The phase diagrams can effectively be described by using a scaling equation with a critical exponent β practically independent of the isotope substitution. A good description of the system was also obtained by using classical equations based on the mean-field theory.