ULTRASONIC VELOCITY AND APPARENT ISENTROPIC COMPRESSIBILITIES IN MIXTURES OF NONELECTROLYTES

Ultrasonic velocities have been determined for binary mixtures of pyri dine + n-alkanol (C-1-C-10) over the whole composition range at 25 deg rees C. The excess isentropic compressibilities K-S(E) and apparent mo lar isentropic compressibilities K-phi S are estimated from these meas urements. The K-S(E) values are negative for all the systems over the complete mole fraction range except pyridine + decanol for which small positive values are obtained. The standard partial molar isentropic c ompressibilities (K) over bar(o) of the alkanols are positive and incr ease linearly with the chain length of the alkanol molecules. It indic ates that a methylene functional group makes a positive contribution t o the expansion coefficient of a solute in these mixtures.