4 ms·

Krypton is relatively cheap because, while it is produced by atmospheric distillation, it is a by-product of oxygen/nitrogen production. The boiling point of ox

Krypton is relatively cheap because, while it is produced by atmospheric distillation, it is a by-product of oxygen/nitrogen production. The boiling point of oxygen is -183 °C, and the boiling point of krypton is -153 °C. This means that when you distill air and obtain liquid oxygen, krypton will necessarily also be obtained as a liquid. Helium, however, has the very low boiling point of -267 °C. Commercial, high-scale production of oxygen doesn't even approach this temperature, so helium will never be distilled and instead be vented as a gas along with a residual air stream. The point is that the price of krypton is actually the marginal cost of producing it from an existing process, while the price of helium will approach the cost of energy required to extract it, which can be calculated and is quite high.

dopamean 8y ago
I've got a really dumb question that maybe you can answer. Keep in mind the last time I was in a chemistry class was 10th grade (half my life ago)... How is the boiling point of any of these elements determined? I cant imagine that we got some helium in its gaseous form and cooled it down below -267 degrees and then heated it up slowly to find out. Is there something about it's atomic makeup that allows that number to just be calculated? Thanks.
- garmaine 8y ago
  > How is the boiling point of any of these elements determined? I cant imagine that we got some helium in its gaseous form and cooled it down below -267 degrees and then heated it up slowly to find out. Why not? That's relatively easy to do in any moderately equipped physics lab.
- thaumasiotes 8y ago
  > Is there something about it's atomic makeup that allows that number to just be calculated? Yes, of course, but sadly we don't know how to do that.
  - dnautics 8y ago
    Helium is extra special because some quantum weirdness happens, e.g. superfluid things
- iaw 8y ago
  No one really answered your question so I'll give it a shot. Increasing the pressure on a gas increases it's boiling point. If you have a lot of pure helium gas and a really good compressor you can increase the pressure until the boiling point is high enough to exceed the temperature of the gas, so now you have a liquid helium at an insane pressure. Next, drop the pressure and stick a thermometer into the liquid. When you hit atmospheric pressure the liquid will be boiling, but boiling liquids don't exceed their boiling point/temperature so helium is going to be waaay cold. You can see this yourself: take a can of dust off or butane, turn it upside down and spray a bit into a shot glass (do not drink or breathe, super toxic). Instead of an aerosol spray a liquid will come out and begin to boil in the process making the glass super cold... So, what's happening here you may wonder? It's chemistry/physics in action. When a pot of water boils on your stove it takes the heat energy from the burner and uses it to change states from liquid to gas. If you pour liquid water onto a piece of hot metal it turns into steam (boiling) while cooling off the metal (removing heat). So when you take any liquid and rapidly raise it above it's boiling point (due to pressure or temperature changes) it will lower the temperature around it in order to obtain the energy it needs to change states. All that being said, compressed helium is the most abundant means of cooling for low-temperature purposes because of these properties. By boiling compressed helium at room temperature and pressure we can make something that super cold -267 degrees, at least while the helium continues to boil.
  - black6 8y ago
    > If you have a lot of pure helium gas and a really good compressor you can increase the pressure until the boiling point is high enough to exceed the temperature of the gas, so now you have a liquid helium at an insane pressure. The critical temperature of Helium is 9.35 °R -- above that it will not be a liquid at any pressure. So we have to go through successive phases of compression (which heats it up), cooling via another cryogen (liquid nitrogen initially, then liquid hydrogen in subsequent passes), and expansion (at the right conditions, because of the oddities of the Joule-Thompson effect[0] for elements like Helium), in order to cool it enough to produce a liquid. [0] https://chemistry.stackexchange.com/questions/61517/reason-for-negative-joule-thomson-coefficient-of-helium-and-hydrogen-at-ntp-cond https://chemistry.stackexchange.com/questions/61517/reason-f...
- magicalhippo 8y ago
  Not only did we do just that, it was done for the first time 110 years ago, in 1908. You can read more and see some pictures here: http://www.dwc.knaw.nl/wp-content/HSSN/2007-10-Van%20Delft-Freezing%20Physics.pdf http://www.dwc.knaw.nl/wp-content/HSSN/2007-10-Van%20Delft-F... Illustration of the helium liquefier at page 403.
- deleted 8y ago
  [deleted]
- salty_biscuits 8y ago
  A lot of these macroscopic features of things are really, really hard to work out from microscopic details from first principles. Things like why is coal black, water wet, etc? Not a stupid question at all.
philipkglass 8y ago
Those are good points. The report from LANL that I edited in after my original rough estimate mentions these issues too. It estimates an electricity requirement of about 170,000 kWh to produce one Mcf (28,317 liters) of helium by atmospheric separation in a dedicated plant. The cost of electricity dominates the overall process cost for helium production via atmospheric separation. In the state with the cheapest industrial electricity, Washington, it would cost nearly 27 cents per liter of helium for the electricity alone. https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a https://www.eia.gov/electricity/monthly/epm_table_grapher.ph...

dopamean 8y ago

I've got a really dumb question that maybe you can answer. Keep in mind the last time I was in a chemistry class was 10th grade (half my life ago)... How is the boiling point of any of these elements determined? I cant imagine that we got some helium in its gaseous form and cooled it down below -267 degrees and then heated it up slowly to find out. Is there something about it's atomic makeup that allows that number to just be calculated? Thanks.

garmaine 8y ago
> How is the boiling point of any of these elements determined? I cant imagine that we got some helium in its gaseous form and cooled it down below -267 degrees and then heated it up slowly to find out. Why not? That's relatively easy to do in any moderately equipped physics lab.
thaumasiotes 8y ago
> Is there something about it's atomic makeup that allows that number to just be calculated? Yes, of course, but sadly we don't know how to do that.
- dnautics 8y ago
  Helium is extra special because some quantum weirdness happens, e.g. superfluid things
iaw 8y ago
No one really answered your question so I'll give it a shot. Increasing the pressure on a gas increases it's boiling point. If you have a lot of pure helium gas and a really good compressor you can increase the pressure until the boiling point is high enough to exceed the temperature of the gas, so now you have a liquid helium at an insane pressure. Next, drop the pressure and stick a thermometer into the liquid. When you hit atmospheric pressure the liquid will be boiling, but boiling liquids don't exceed their boiling point/temperature so helium is going to be waaay cold. You can see this yourself: take a can of dust off or butane, turn it upside down and spray a bit into a shot glass (do not drink or breathe, super toxic). Instead of an aerosol spray a liquid will come out and begin to boil in the process making the glass super cold... So, what's happening here you may wonder? It's chemistry/physics in action. When a pot of water boils on your stove it takes the heat energy from the burner and uses it to change states from liquid to gas. If you pour liquid water onto a piece of hot metal it turns into steam (boiling) while cooling off the metal (removing heat). So when you take any liquid and rapidly raise it above it's boiling point (due to pressure or temperature changes) it will lower the temperature around it in order to obtain the energy it needs to change states. All that being said, compressed helium is the most abundant means of cooling for low-temperature purposes because of these properties. By boiling compressed helium at room temperature and pressure we can make something that super cold -267 degrees, at least while the helium continues to boil.
- black6 8y ago
  > If you have a lot of pure helium gas and a really good compressor you can increase the pressure until the boiling point is high enough to exceed the temperature of the gas, so now you have a liquid helium at an insane pressure. The critical temperature of Helium is 9.35 °R -- above that it will not be a liquid at any pressure. So we have to go through successive phases of compression (which heats it up), cooling via another cryogen (liquid nitrogen initially, then liquid hydrogen in subsequent passes), and expansion (at the right conditions, because of the oddities of the Joule-Thompson effect[0] for elements like Helium), in order to cool it enough to produce a liquid. [0] https://chemistry.stackexchange.com/questions/61517/reason-for-negative-joule-thomson-coefficient-of-helium-and-hydrogen-at-ntp-cond https://chemistry.stackexchange.com/questions/61517/reason-f...
magicalhippo 8y ago
Not only did we do just that, it was done for the first time 110 years ago, in 1908. You can read more and see some pictures here: http://www.dwc.knaw.nl/wp-content/HSSN/2007-10-Van%20Delft-Freezing%20Physics.pdf http://www.dwc.knaw.nl/wp-content/HSSN/2007-10-Van%20Delft-F... Illustration of the helium liquefier at page 403.
deleted 8y ago
[deleted]
salty_biscuits 8y ago
A lot of these macroscopic features of things are really, really hard to work out from microscopic details from first principles. Things like why is coal black, water wet, etc? Not a stupid question at all.

philipkglass 8y ago

Those are good points. The report from LANL that I edited in after my original rough estimate mentions these issues too. It estimates an electricity requirement of about 170,000 kWh to produce one Mcf (28,317 liters) of helium by atmospheric separation in a dedicated plant. The cost of electricity dominates the overall process cost for helium production via atmospheric separation. In the state with the cheapest industrial electricity, Washington, it would cost nearly 27 cents per liter of helium for the electricity alone. https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a https://www.eia.gov/electricity/monthly/epm_table_grapher.ph...