ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 45, Number 4
JKCSEZ 45(4)
August 20, 2001 

The existing vapor pressure measurements reported in the literature for parahydrogen between the triple point and the critical point have been employed to establish the constants and exponent of the following equation in the form of reduced vapor pressure and reduced temperature:
ln P_r= 2.64 - 2.75 / T_r + 1.48129 ln T_r + 0.11 T⁵_r
Only the normal boiling point (T_b = 20.268 K), the critical pressure (P_c = 1292.81 kPa), and the critical temperature (T_c= 32.976 K) are necessary to calculate the vapor pressure for an overall average deviation of 0.21% for 153 experimental vapor pressure data.