Vapor pressures of n-heptane determined by comparative ebulliometry

Abstract

The vapor pressures of n-heptane have been measured using comparative ebulliometry with water as the reference substance. The measurements cover the temperature and pressure range (372 K and 102 kPa) to (537 K and 2621 kPa) and were correlated by a Wagner-type equation with a standard deviation of 16 Pa in the vapor pressure. The critical pressure was treated as an adjustable parameter, and the value p c = 2734 kPa was obtained using a selected critical temperature, T c = 540.13 K. The calculated normal boiling temperature is T b = 371.552 K, and an extrapolation to the triple point pressure at T tp = 182.59 K predicts a pressure, p tp = 0.178 Pa.