Some Favorite Cryogens
The proper term for a very cold liquid with a boiling point below 123 K is cryogen. You can say cryogenic liquid if you want to, but that is not cool. Cryogens are cool.
Below are some favorite cryogens, their normal boiling points (NBP) at atmospheric pressure, and a couple of important properties.
| Cryogen |
NBP |
NBP |
Density |
Heat of Vaporization |
Expansion Ratio |
Note |
| K |
deg F |
kg/m3 |
J/g |
Gas/Liquid |
||
| Water |
373 |
+212 |
958 |
2,257 |
1,624 |
Not a cryogen, but good for reference |
| Methane |
112 |
-259 |
424 |
512 |
658 |
Natural gas is about 87% methane |
| Oxygen |
90 |
-297 |
1,141 |
213 |
877 |
Slightly blue color |
| Argon |
87 |
-303 |
1,394 |
162 |
858 |
Earth's atmosphere is 0.93% argon |
| Air |
79 |
-318 |
874 |
205 |
743 |
About 80% nitrogen & 20% oxygen |
| Nitrogen |
77 |
-321 |
807 |
199 |
707 |
All around favorite cryogen |
| Neon |
27 |
-411 |
1,206 |
86 |
1,471 |
Air is 0.0018% (18 ppm) neon |
| Hydrogen |
20 |
-423 |
71 |
443 |
865 |
Para-Hydrogen |
| Helium-I |
4.2 |
-452 |
125 |
21 |
768 |
Helium-4 |
| Helium-II |
2.177 |
Superfluid, below lambda point |
||||
| Helium-3 |
3.19 |
58.9 |
15.87 |
At 1.65 K |
The temperatures are given in the units of kelvin (K) or degree Fahrenheit (deg F). Please stick with either one of these and much preferably kelvin (K). Degree Celsius (deg C) is okay if you are dealing with a chemist but degree Rankine (deg R) is strictly forbidden (you know who you are....get with it).
Density (kg/m3) is density of the saturated liquid. Saturated means that the cryogen is happy, or at least in acceptance of, its current situation and that the weather, at least the atmospheric pressure, is stable. The heat of vaporization (J/g) is an enthalpy. It is the energy (J or joules) required to vaporize an amount of liquid (g or gram).
One important point is the lowest temperature for solid-state matter as we know it. That would be absolute zero or 0 K (-459.67 deg F or -273.15 deg C). Absolute zero is useful because it makes cryogenics very special. On the hot side: How hot can it get, how hot can something be? It is rather unlimited and ambiguous. But on the cold side there is a limit, a big round zero limit. And getting closer and closer to it are many challenges worthy of great prizes.
Liquefied Natural Gas (LNG)
The use of LNG (and methane) is really picking up steam in the USA and around the world. LNG is used for fuel stored in gaseous or liquid form. Also, LNG (mostly CH4) is used to make hydrogen (H2). Here are a few of the main publications tracking the industrial side of things in the area of LNG.
LNG Industry
GasWorld LNG News
EnergyGlobal LNG News
LNG Journal
Here are some good videos that show and explain the general effects associated with boiling liquids such as liquid nitrogen:
Cup of LN2
Boiling LN2 and mixtures
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| Much of the universe is close to absolute zero. |
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| Just the best Hubble telescope picture ever! |