Gas in Cold Weather: The Myth of “Fractioning”

I appreciate the clear explanation. Thanks, HJ

Hi, Dan,

You’re welcome. Glad that it was clear. It’s a bit complicated, but hopefully worth knowing.

HJ
Adventures in Stoving

Fractionation is a chemistry/engineering/industry term that is used to describe the separation of components from a mixture. Commonly based on their relative vapor pressures, but other techniques such as chromatographic or such also are encompassed. It does not mean separation of a pure component, just separation and enrichment of a phase with respect to at least one component.

As such, fractionation is occuring. This is mostly used in industry to describe distillation systems with multiple stages to purify products from mixtures.

I have never heard the myth that all of one species could vaporize, but it wouldnt surprise me to hear that be spewed around by the same folks that think the cannister pressure has something to do with how full it is. Most persons cannot be expected to have had the courses necessary to understand what is occurring.

Seems that a common term, is actually being mis-applied to that myth, but I would say that fractionation is occuring.

There's also an extended technical article on canisters in cold weather at
http://www.backpackinglight.com/cgi-bin/backpackinglight/effect_of_cold_on_gas_canisters.html
Full explanations, graphs etc.

Cheers

Indeed there is Roger. I wonder if that was HJ's source?

I wonder if that was HJ’s source?

Most certainly — at least in part. I’ve read all of Roger’s articles on bushwalking.org.au, his articles here, and the article he co-wrote with you. I’ve read other articles in magazines such as Off Belay. I’d have to say that the Gas in Cold weather article here on BPL is one of the best if not the best. I also have my university studies which give me some background albeit a bit old now. My post was in response to a question posed to me on WhitneyZone.com. I responded from memory. I’m sure I drew on all of the things I’ve mentioned, above; there may be some other influences. Perhaps an old Backpacker Magazine article or two. There was a day when Backpacker was a very thorough and in depth magazine.

HJ
Adventures In Stoving

Fractionation is a chemistry/engineering/industry term

Yes it is. My choice of the word “fractioning” to describe the myth may not have been the best. I was just trying to convey the idea of a simple fraction.

In the case of a 100g canister with a 70/30 butane propane mix, the simple fraction would be 3/10ths (30g of propane out of a total of 100g). The myth is than only that fraction (3/10ths) that is propane will burn off. The reality is that far more will burn. Hopefully the posting was clear even if the use of the word “fractioning” was unclear.

HJ
Adventures In Stoving

Fair enough. I guess I should be happy that you have taken the time to provide another source of factual information, given the amount of misinformation out there that gets mindlessly recycled. Keep going.

Well, and I owe you and Roger quite a debt of thanks for the mathematical portion of the article alone. Perhaps I could have eventually pieced together the overall mechanics of gas in cold weather from other sources, but I never could have done the math. I have committed to memory that the boiling point at sea level of a 70/30 butane/propane or a 80/20 isobutane/propane mix is about 0F/-18C. Those are very important numbers for inverted remote canister stove users in cold weather.

HJ
Adventures in Stoving