Talk:Heliox

Maintenance tags

I've added such references as I thought were relevant - do I now remove the Unreferenced tag?

Is there enough here to remove the diving-stub tag - or is that best left in to encourage further contribution? RexxS (talk) 02:31, 10 January 2008 (UTC)

Hey there RexxS, glad to see you've joined the SCUBA project. I removed the unreferenced tag, you did an excellent job referencing the article. The "stub" tag should probably go to. If you read here, you'll see that this article is considerably longer than what is normally viewed as a "stub". If you read here, you'll see that anyone can remove a stub tag, you don't need special powers. Just click on Edit this page, and pull it out of there! If you feel the article could still use further expansion, you can add {{expand}}. It's a tag that requests expansion, but doesn't classify the article as "stub". Put it in place of the stub tag. I'll leave you to it - go for it! Again, great work, happy editing! Keeper | 76 16:34, 10 January 2008 (UTC)

Thanks for your help and guidance - it's much appreciated. I think that the section on Heliox diving could be expanded to emphasise the differences between Heliox and trimix - or maybe that's best done in the trimix page? Hopefully the expand tag will attract some more content. RexxS (talk) 23:15, 10 January 2008 (UTC)

"Low density of the gas???"

The article states:

"Heliox has been used medically since the 1930s, and . . . its range of medical uses has since expanded greatly, mostly because of the low density of the gas."

I'm neither a chemist nor physicist -- but given a certain amount (mass) of a gas, doesn't its density depend on its volume (or equivalently, on its pressure), either of which is vastly a matter of choice rather than a property of the gas itself? In which case, describing a gas as just plain having a "low density" makes no sense.

Or, what am I missing?Daqu (talk) 04:23, 7 October 2008 (UTC)

I think the easiest way to explain is point to the interesting fact that at a given pressure and volume, every gas contains the same number of molecules (see Avogadro's Law). It then follows that, if we think about breathing a gas at normal pressure, the mass of a litre of a gas will be proportional to its molecular weight - and therefore so will its density. In this case, I hope you can see that comparing He (molecular weight 4) to N₂ (molecular weight 28) will mean that in a given application, heliox will have a lower density than air.

On the other hand, I may be missing your point - you say pressure, volume, etc. is a matter of choice. In fact it isn't. When we breathe, we have to breathe the gas at ambient pressure - that's atmospheric pressure (unless we're scuba diving or an astronaut) and the volume of gas we breathe depends on our lungs and the body's requirement for oxygen. In other words, a lungful of heliox will always weigh less than a lungful of air. Couple that with the section Heliox#Medical uses, and you can see why heliox has medical uses which depend on the low density of the gas. If you like, when a gas is described as "low-density", it is always going to be understood within a context, otherwise - as you are point out - density as a property would make no sense. --RexxS (talk) 13:28, 7 October 2008 (UTC)