Critical Temperatures and Pressures for some Common Substances

Critical temperatures and pressures for some common substances like air, alcohol, ether, oxygen and more.

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Gases can be converted to liquids by compressing the gas at a suitable temperature. However, they become more difficult to liquefy as the temperature increases because the kinetic energies of the particles that make up the gas also increase. At the critical temperature they cannot longer be liquified.

Critical Temperature: The temperature which above, a substance can not exist as a liquid, no matter how much pressure is applied. Every substance has a critical temperature.
Critical Pressure: The pressure required to liquify a substance vapor at its critical temperature
Critical point: The end point of the pressure-temperature curve that designates conditions under which a liquid and its vapor can coexist. At higher temperatures, the gas cannot be liquefied by pressure alone. At the critical point, defined by the critical temperature T_c and the critical pressure p_c, phase boundaries vanish.
Triple point: The temperature and pressure at which the three phases (gas, liquid, and solid) of a substance coexist in thermodynamic equilibrium.

The table below shows critical temperature and pressure for some common substances, together with boiling temperature.

Critical_temperature_pressure

See Triple point for listing of triple point values for common substances.

Substance	Critical temperature		Critical pressure		Boiling temperature (1 atm)
Substance	[°F]	[°C]	[psi], [lb/in²]	[bar]	[°F]	[°C]
Air	-220.94	-140.52	549.08	37.858	-	-
Ammonia (NH₃)	270	132.4	1636	112.8	-27.4	-33
Argon	-188	-122	705.6	48.7	-302.5	-185.8
Butane	305.6	152	550.4	38	32	0
Carbon-dioxide (CO₂)	87.8	31.2	1071.6	73.8	-110	-79
Carbon-monoxide (CO)	-220.5	-140.3	507.5	35	-310	-190
Chlorine	291	144	1118.7	77.1	-29.3	-34
Decane	653	345	301.7	20.8	345	174
Dowtherm A			465	32.1
Ethane	90.0	32.2	708	48.9	-127.4	-88.5
Ethanol (alcohol)	467	242	914	63	173	78.4
Ethylether	381	194	522	36	94.2	34.6
Ethylene	48.9	9.4	735	50.7	-272.6	-169.2
Fluorine	-200	-129	808.5	55.8	-307	-188
Helium	-456	-271	33.2	2.3	-452	-269
Hydrogen (H)	-400	-240	188.2	13.0	-423	-253
Hydrogen Chloride	125	51.6	1198	82.7	-121.1	-85.1
Isobutane	274	135	529.2	36.5	10.9	-11.7
Isobutylene	293	145	580	40.0	19.6	-6.9
Isononane	590	310	335.1	23.1	303	151
Methane	-117	-82.6	673.3	46.5	-259	-162
Nitrogen (N)	-232.6	-147	492.4	34.0	-321	-195
Nitrous Oxide (N₂O)	97.4	36.4	1047.6	72.3	-127	-88.5
Oxygen (O₂)	-181.5	-118.6	732	50.5	-297	-183
Phosgene			823.2	56.8	46.9	8.3
Propane	206.1	96.7	617.4	42.6	-44	-42
Propylbenzene	689	365	464.2	32	319	159
Propylene	198	92.4	670.3	46.3	-54	-48
Refrigerants
Undecane	691	366	287.2	19.8	385	196
Water	705	374	3206.2	220.5	212	100

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Critical Temperatures and Pressures for some Common Substances

Critical temperatures and pressures for some common substances like air, alcohol, ether, oxygen and more.

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