Description:
<jats:p>The binary liquid system 2-methylpyridine+D2O has a closed miscibility loop at 1 atm. With increasing pressure the size of the two-phase region shrinks until the upper and lower consolute points merge at ∼101°C and ∼200 atm (at which point the critical mole fraction of D2O is ∼0.91). Such a critical point at the top of the miscibility dome is of a special type that has been predicted to have a weakly divergent adiabatic compressibility. Ultrasonic measurements at 1 MHz do not confirm this prediction, and possible reasons for the discrepancy between theory and experiment are discussed.</jats:p>