AbstractExperimental equilibrium vapor and liquid compositions are reported for the hydrogen‐methane system at −150°, −200°, and −250°F. and at pressures of 500 to 4,000 lb./sq. in. The ternary system hydrogen‐methane‐propane was studied at 0°, −100°, and −200°F. at 500 and 1,000 lb./sq. in. Phase compositions were determined for a limited number of similar conditions for the hydrogen‐methane‐propylene and hydrogen‐methane‐ethylene‐e