Isotherms of methane have been determined for a series of temperatures between 0º and 200º C. by Keyes, Smith, and Joubert, and by Keyes and Burks, but, inasmuch as the highest pressure reached at 0º in these researches was 130 atmospheres, and the isotherm as extrapolated from their derived equation did not indicate the expected pv A minimum at about 150 atmospheres ( vide 3), it was deemed advisable to extend the measurements at 0º to 220 atmospheres, and also to determine the isotherm at 20º C. Olszewski was the first to measure the vapour pressures of methane, down to a temperature of –203º C., but his results are chiefly of historical interest. Determinations of the vapour pressures of the liquid between –182º and –150º C. have been made by Stock, Henning, and Kuss, but, apart from a solitary measurement of the triple-point by Crommelin, no modern work seems to have been done on the vapour pressures of the solid. The range between –178º and the critical temperature has been covered by Keyes, Taylor, and Smith in a comprehensive paper upon the thermodynamic properties of methane.

The investigation of two- and three-phase equilibria at low temperatures and high pressures appears hitherto to have been limited almost exclusively to single-component systems. A very few researches on binary systems at low temperatures, such as those of HOLST and HAMBERGER* on argon and nitrogen, and of KUENEN and CLARK, of KUENEN, VERSCHOYLE and VAN URK, and of BARNETT, DODGE and DUNBAR§ on oxygen and nitrogen have been published. No other work on binary systems at low temperatures and high pressures can be traced, and the field of ternary systems at low temperatures would seem to be entirely unexplored. The present researches concern a ternary system which is of importance in the consideration of the technical production of hydrogen by low temperature methods. Both the ternary system itself and the two binary systems, carbon monoxide-hydrogen and nitrogen-hydrogen, were investigated under conditions where the temperature lies well above the critical temperature of one component, but well below that of the other component (or components).