Vapor pressures of the methanes

Abstract

Experimental meas urements, not previously reported in detail, of the vapor pressure of CH, and the differe nces in vapor press ures of CH. and the deuterom ethanes below the normal boiling point are presented. A critical revi ew of the literature relating to the vapor pressures of m ethane and the deu teromethanes is given. On the basis of the experim ental measurem ents and t he previous literature t he following best values are assigned to fix ed points on the vapor pressure curves. . Th e vapor-press ure ratios of the isoto pic m etha nes for m a nearl y geo metri c p rogressio n wi t h in creas ing d eute rium substitution. Dev ia t io ns of t heir mix t lll'eS fr om ideal solu t io ns arc very s m·a ll. A Review of the Vapor Pressure of Methane and the Deuteromethanes MethaneThe vapor pressure of solid and liquid methan e has been determined in various tempera! ure ranges by many investigators, and , in addi tion , t her e have b ee n sever al summari es of t he pu bli shed da ta. S. F. [12] and by Bl'ickwedde and Scott of t he National Bureau of tandards (section 2 of t his pap er ). D cterminations of t.h e tripl e poi.nt as Ii tcd in table 1 provide a fixed point t hrough whi ch an equation for the da ta should pass. Of Lh e reported determi ll ations, t he exLensiv e da ta from Clusiu ' labor atory ap pear to be besL l'epresen ted b y Lhe values 90.67 ± 0.03° K and 87.4 ± 0.1 mm , which were determin ed from a sLudy of the melLin g temperatul'e as a fun cLion of pressure. Th e value 90.660 ± 0.005° K and 87.60 ± O.I O mm. were foun d by Brickwedde and Scott wi Lh a carefully purified sample. The besL values of t he triple poin L Lemperature and press ure appeal' 1,0 be 90.66 ± 0.01 ° K and 87.50 ± 0.10 mm .In an attempt to r emedy this deficien cy t his r eview has been prepared in which the data from variou sources h ave been compared including those describ ed in section 2, previously unpublished, and available to non e of the previous reviewers except perhaps Rossini. An attemp t has been made to find equations which fit well t he best available data and at the same time pass t hrough selected b est values for the triple point, normal boiling point, and critical poin t.

Thermophysical properties of methane: Virial coefficients, vapor and melting pressures

“…At first we allowed the triple-point pressure in (4) to appear on the right as a least-squares coefficient, finding a value in agreement with [11], table 1. Thereafter we used (4) as written, constrained to the triple point.…”

New experimental sublimation energy measurements for some relevant astrophysical ices

“…These experiments (Armstrong et al 1955;Jones 1960;Stephenson & Malanowski 1987) use an experimental apparatus based in an evacuated vessel surrounded by a bath of liquid air in a Dewar flask whose temperature is given by a platinum resistance thermometer. The vacuum in the vessel is produced by a vacuum pump, and the final pressure is measured with a differential oil-manometer ranging pressures from 10 −1 to 10 3 mbar.…”

Temperature Dependence of the Liquid-Vapor Isotopic Fractionation Factors in CD3H-CH4 and CD3F-CH3F Mixtures

“…Two sys tems were chosen for investigation, deuterium substi tution in methane and methyl fluoride. In the case of methane there is the usual red shift of the C -H vibra tions in the liquid phase compared with the vapor with the result that deuteromethanes have higher va por pressures than the protium isomer at high temper atures and show the cross over at low temperatures [20]. In the case of methyl fluoride the D/H VPIE is normal [21].…”