Of course, a search for “dry ice” doesn’t work…
With the news of record lows in the US I got to wondering - does it ever get cold enough on Earth for carbon dioxide to snow out of the air? In other words, is is possible to have snow made of dry ice instead of water ice? Does it ever get that cold anywhere on the planet (outside of laboratories)?
If it is possible, has this ever been known to actually happen? (I’m assuming the most likely place is Antarctica)
Thought your question was interesting. This scientist from Argonne National Laboratory says the answer is no, because of the very low partial pressure of CO2 in normal atmosphere.
Surprising. I would’ve guessed yes, in Antarctica anyway.
Dry Ice forms at -109F. The record low at Vostok Station in Antarctica is -128F. So it gets cold enough. But CO2 concentration in the air is extremely low like only about 0.04% so I don’t know it that concentration is enough to have the CO2 settle out of the air.
The ‘frost’ produced by spraying compressed gas may contain a large percentage of CO2 ‘dry ice’. Even at the low concentrations in the atmosphere it will form. Perhaps in very cold environments the concentration of CO2 is much lower, or it needs to form in warmer air or on a warmer surface.
I suppose hypothetically you could have a volcano erupt in Antarctica and expel a quantity of CO2 that settles into a really cold valley that then becomes encrusted with dry ice… but if normal atmosphere just doesn’t have a high concentration of CO2 then I can see it not snowing dry ice. After all, when the temperature drops below the freezing point of water it doesn’t automatically snow, there has to be enough water vapor in the air for it to happen.
I’ve been looking for the cite on this and can’t find it, which makes me suspect its accuracy. Unless you spray CO2 I can’t see how any frost would contain any amount of frozen CO2 that exceeds the tiny percentage in the air. Since CO2 would have to go from a gas to solid form, I think it would probably reduce in volume significantly and nothing more than microscopic crystals could be produced. That’s probably the maximum effect you could get with a normal atmosphere at extremely cold temperatures.
I assume he was talking about CO2. Even so, Im pretty sure it’s not true. In order to get dry ice out of a tank, you must have a tank designed with a dip stick that pulls the liquid from the bottom. Since the stuff from other tanks is allready a gas, I have trouble believing mere expansion is enough to cause it to freeze.
You are incorrect, sir. Sudden expansion cools a gas (this is actually how most refrigerator works, including the one in your home), and if the expansion is sudden enough, and large enough, it will indeed induce freezing. Conditions have to be right, of course, but it will work.
a compressed gas expanding after an orifice will cool significantly. there are devices (orifice, valve and bag) that can produce small volumes of solid carbon dioxide from an ordinary cylinder of compressed carbon dioxide gas.
I understand the expansion of gases. I’m not certain that the conditions can be achieved from the expanding of gases from a tank. You will certainly get nowhere if you are trying to get a use able quantity of dry ice out of a CO2 tank. The tank gets cold if you really let it go fast, but I need a cite that it gets that cold.
I have used these devices, but they do not work with an ordinary compressed gas tank. You need a tank with a dipstick to get to the liquid at the bottom of the tank. What causes the gas to freeze is the heat of vaporization as the liquid quickly evaporates when it exits the regulator.