How are gasses, such as helium, separated from other gasses and added to a canister?
In: Chemistry
It depends on the gas. Thought the most used way is by compression and boiling. If you take a mix of gasses, like the air you’re breathing now, and you compress it a lot it will turn into a liquid. Compress any gas enough and they will become a liquid.
Once all the gasses are in liquid form, you begin to add heat. Different gasses will boil away at different times. The “lighter” the gas is the quicker it will boil away. All you have to do is capture that gas that was boiled off and you have a nearly pure concentration of that gas.
Though for helium the steps are a little different, but it follows essentially the same process of using the temperature and pressure to separate the gasses and collect them.
Gases can be separated similarly to the way some mixtures of liquids are separated,
by taking advantage of their different characteristics.
Some liquids are separated by distillation: different boiling points.
A solution contains some liquid A and some liquid B.
Liquid A has a boiling point lower than the boiling point of liquid B.
If you heat the solution to the boiling point of liquid A, A will become a gas, and you can cool the gas and collect liquid A.
You can continue heating the solution to the boiling point of B, and separate and collect B as well.
With gases like helium, oxygen, nitrogen, they have different boiling points as well, so we take advantage of that by *cooling* the mixed gas. Cool air enough and the oxygen will condense out (at 90 kelvin), and you can collect it. Keep cooling the gas and the nitrogen will condense out (63 kelvin) and you can collect *it*.
Helium is very light, so you can centrifuge it and keep the lighter gas. It also has a super-low boiling point, so you can cool it to cryogenic temperatures. All the other gasses will turn to liquid, that gas that’s left is helium.
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