Experimental melting and vapor pressures of methane

Abstract

Thirteen melting pressures to 210 atm are represented by the Simon equation with a root mean square deviation of 0.05 atm (0.08 per cent). This representation is highly sensitive to the triple point temperature, yielding 90.680 K (IPTS-1968). These pressures agree within 0.5 per cent with the less precise data of one other investigator at temperatures above 93 K. One hundred and five vapor pressures from the triple point to the critical point are represented by a new, non-analytic equation with a root mean square relative deviation of 0.01 per cent. The derived triple point pressure is 0.1159 atm. At the assigned critical point temperature of 190.53 K the pressure is 45.356 atm. Deviations of some of the data from other sources exceed one per cent at T