4 ms·
Hermetically sealed by definition is airtight, i.e. "excludes the passage of air, oxygen, or other gases". [1] With that said, the diffusion rate depends on bot
by Triesault 8y ago
Hermetically sealed by definition is airtight, i.e. "excludes the passage of air, oxygen, or other gases". [1] With that said, the diffusion rate depends on both the properties of both the seal and the gas.
[1] https://en.wikipedia.org/wiki/Hermetic_seal https://en.wikipedia.org/wiki/Hermetic_seal
- garmaine 8y agoVery few air seals protect against helium, the smallest gas. Most materials, even metals, are like sponges to helium. It'll seep through slowly.
- hanniabu 8y agoCase in point, helium filled balloons that deflate over a couple days.
- yetihehe 8y agoAir filled balloons also deflate over a couple days.
- namibj 8y agoCompare with aluminium coated foil. They don't deflate that fast.
- Keloo 8y agoOr intestines of cattle. https://en.wikipedia.org/wiki/Zeppelin https://en.wikipedia.org/wiki/Zeppelin Early Zeppelins used rubberised cotton for the gasbags, but most later craft used goldbeater's skin, made from the intestines of cattle
- jammi 8y agoThat’s just because rubber balloons are extremely porous, especially when stretched. They don’t hold other gases well either.
- ricardobeat 8y agoHelium balloons are commonly made out of Mylar instead of rubber, and can keep inflated for weeks.
- Cthulhu_ 8y agoThe type intended for keeping around / in a shop for longer time are, but the children's party type often are inflated on the spot.
- lb1lf 8y agoCompletely irrelevant, yet amusing: At a former employer, we had access to what can only be described as unlimited supplies of hydrogen. This led - in addition to lots and lots of eardrum-splitting workshop pranks - the occasional kids' party balloons being inflated with hydrogen. (As it was free, which He definitely isn't. HS&E be damned.) A then colleague of mine claimed they'd cracked a window and caused instant panic at his son's birthday party when a bright spark decided to put a balloon to a lit candle to show the other kids it'd pop. I doubt the cracked window (given a standard party balloon is pretty small - and a cracked window would likely mean lots of -ahem- eardrum deficiency in the assembled crowd) - but I can imagine it got the kids' attention all right when the balloon more or less exploded. (We did crack a couple of windows in the workshop, though - you'd be amazed at the bang a litter bag filled with a hyd/ox mixture can produce if set alight.)
- hazeii 8y agoHydrogen alone just makes a soft pop; as you say, for a bang it needs to be mixed with oxygen prior to ignition. >you'd be amazed at the bang a litter bag filled with a hyd/ox mixture can produce if set alight. Try a large garbage bag with oxyacetylene mix (do not try this at home).
- Florin_Andrei 8y agohttps://www.youtube.com/watch?v=YDls3_v_2oI https://www.youtube.com/watch?v=YDls3_v_2oI
- zik 8y agoI thought hydrogen was the smallest gas, not helium.
- Wingman4l7 8y agoDepends on your definition of smaller, but apparently it's not clear-cut: https://www.quora.com/Which-element-is-bigger-an-atom-of-hydrogen-or-of-helium https://www.quora.com/Which-element-is-bigger-an-atom-of-hyd...
- chopin 8y agoHydrogen normally comes as a molecule (H2), not an atom.
- garmaine 8y agoCorrect, but also just as importantly the He atom has both a higher nuclear charge and a full valence shell, which pulls the electrons in more tightly. I’d have to look it up but I believe a single He is even smaller than atomic hydrogen or at least comparable. Edit: looked it up and yes, helium is smaller than atomic hydrogen.
- Wingman4l7 8y agoI was about to correct you and say that hydrogen is the smallest, but apparently, hydrogen's atomic radius is actually a bit bigger. Helium's radius is smaller due to the larger charge of the nucleus making for a tighter electron cloud.
- jankotek 8y agoHydrogen creates molecules H2.
- manojlds 8y agoI too had the same thought, and then thought maybe hydrogen molecule is being considered. Read up to see that hydrogen atom has bigger radius. TIL.
- Florin_Andrei 8y agoYup. Larger atomic radius due to less nuclear charge, and it's only stable in molecular form - H2.
- danburbridge 8y agoHelium can cause problems with the metals containing fusion reactors - He bubbles can get inside the metal structure and weaken it considerably: "The sun makes energy by fusing hydrogen atoms, each with one proton, into helium atoms, which contain two protons. Helium is the byproduct of this reaction. Although it does not threaten the environment, it wreaks havoc upon the materials needed to make a fusion reactor. "Helium is an element that we don't usually think of as being harmful," said Dr. Michael Demkowicz, associate professor in the Department of Materials Science and Engineering. "It is not toxic and not a greenhouse gas, which is one reason why fusion power is so attractive." However, if you force helium inside of a solid material, it bubbles out, much like carbon dioxide bubbles in carbonated water. "Literally, you get these helium bubbles inside of the metal that stay there forever because the metal is solid," Demkowicz said. "As you accumulate more and more helium, the bubbles start to link up and destroy the entire material."" https://phys.org/news/2017-11-fusion-energy.html https://phys.org/news/2017-11-fusion-energy.html
- khafra 8y agoSometimes, definitions aren't the most mechanically sound constructs available.
- deleted 8y ago[deleted]
- jhoechtl 8y agoWell, air is also compound of rare gases of which Helium is one.