propane/butane heavier or lighter than air?
Steve Holzworth
This is a branch of a discussion from rec.boats about cook stoves.
There is a disagreement about the relative densities and energy
content of assorted stove fuels, including butane, propane, and alcohol.
I was under the impression that propane is heavier than air (which makes
using it on a boat an exercise in caution). Butane, I'm not sure about.
I was also under the impression that propane and butane burn with a hotter
flame than alcohol. Any chemists out there care to comment (references
would be great)?
I know that butane and propane are both hydrocarbon gasses, and I seem
to remember hearing that butane is lighter than air and propane is
heavier than air.
--
Steve Holzworth
s...@unx.sas.com "Do not attribute to poor spelling
SAS Institute x6872 That which is actually poor typing..."
Open Systems R&D VMS/MAC/UNIX - me
Cary, N.C.
Uncle Al
Steve Holzworth wrote:
>
> This is a branch of a discussion from rec.boats about cook stoves.
> There is a disagreement about the relative densities and energy
> content of assorted stove fuels, including butane, propane, and alcohol.
>
> I was under the impression that propane is heavier than air (which makes
> using it on a boat an exercise in caution). Butane, I'm not sure about.
> I was also under the impression that propane and butane burn with a hotter
> flame than alcohol. Any chemists out there care to comment (references
> would be great)?
>
> I know that butane and propane are both hydrocarbon gasses, and I seem
> to remember hearing that butane is lighter than air and propane is
> heavier than air.
1) Dry air at STP has an average molecular weight of 29.
2) The molar volume of all gases at STP (zero order approximation) is
22.4 liters.
3) Now you can calculate how much heavier propane and butane are than
air.
--
Uncle Al Schwartz
Uncl...@ix.netcom.com ("zero" before @)
http://pw2.netcom.com/~uncleal0/uncleal.htm
http://www.ultra.net.au/~wisby/uncleal.htm
http://www.guyy.demon.co.uk/uncleal/uncleal.htm
(Toxic URLs! Unsafe for children, Democrats, and most mammals)
"Quis custodiet ipsos custodes?" The Net!
John Vinson
On Mon, 2 Feb 1998 21:49:36 GMT, s...@unx.sas.com (Steve Holzworth)
wrote:
>This is a branch of a discussion from rec.boats about cook stoves.
>There is a disagreement about the relative densities and energy
>content of assorted stove fuels, including butane, propane, and alcohol.
Propane and butane, as liquids, are a LOT heavier than air; they're
also gasses at room temperature and ambient pressure. With molecular
weights of 42 and 58 respectively, they are both a good bit denser
than air (average mw 29).
When I lived in Sallisaw, Oklahoma in about 1959, a propane storage
tank on a hill west of town had a valve break off. A cloud of propane
flowed several hundred yards downslope onto the highway. A guy drove
into the cloud, stopped, and made the mistake of starting the car
again.
The explosion rattled the windows in my house about four miles away.
They found out from the next of kin how many people had been in the
car.
Peter Mott
Steve Holzworth wrote:
>
> This is a branch of a discussion from rec.boats about cook stoves.
> There is a disagreement about the relative densities and energy
> content of assorted stove fuels, including butane, propane, and alcohol.
>
> using it on a boat an exercise in caution). Butane, I'm not sure about.
> I was also under the impression that propane and butane burn with a hotter
> flame than alcohol. Any chemists out there care to comment (references
> would be great)?
>
> I know that butane and propane are both hydrocarbon gasses, and I seem
> to remember hearing that butane is lighter than air and propane is
> heavier than air.
I can't resist a question that I know the answer to...
air = 80% N2 + 20% O2 = 28(0.8) + 32(0.2) = 28.8
propane = C3H8 = 44
butane = C4H10 = 58
--> Both butane and propane are heavier than air.
Energy content is a more complicated. As a camper, I would
be concerned with the energy content based on the weight and size
of the thing I carry. Propane can be liquified, but the tank
will be heavier because it needs to be pressurized. This then
becomes an engineering question.
Peter Mott
(sorry about the double post; I mistyped.)
Stewart Rowe
In a previous article, Uncl...@ix.netcom.com (Uncle Al) says:
>Steve Holzworth wrote:
>>
>> This is a branch of a discussion from rec.boats about cook stoves.
>> There is a disagreement about the relative densities and energy
>> content of assorted stove fuels, including butane, propane, and alcohol.
>>
>> I was under the impression that propane is heavier than air (which makes
>> using it on a boat an exercise in caution). Butane, I'm not sure about.
>> I was also under the impression that propane and butane burn with a hotter
>> flame than alcohol. Any chemists out there care to comment (references
>> would be great)?
>>
>> I know that butane and propane are both hydrocarbon gasses, and I seem
>> to remember hearing that butane is lighter than air and propane is
>> heavier than air.
>
> 1) Dry air at STP has an average molecular weight of 29.
> 2) The molar volume of all gases at STP (zero order approximation) is
>22.4 liters.
> 3) Now you can calculate how much heavier propane and butane are than
>air.
>
>--
>Uncle Al Schwartz
>Uncl...@ix.netcom.com ("zero" before @)
>http://pw2.netcom.com/~uncleal0/uncleal.htm
>http://www.ultra.net.au/~wisby/uncleal.htm
>http://www.guyy.demon.co.uk/uncleal/uncleal.htm
> (Toxic URLs! Unsafe for children, Democrats, and most mammals)
>"Quis custodiet ipsos custodes?" The Net!
>
Not if he is not a chemist.
Stewart Rowe sr...@tso.cin.ix.net
Peter Mott
Steve Holzworth wrote:
>
> This is a branch of a discussion from rec.boats about cook stoves.
> There is a disagreement about the relative densities and energy
> content of assorted stove fuels, including butane, propane, and alcohol.
>
> I was under the impression that propane is heavier than air (which makes
> using it on a boat an exercise in caution). Butane, I'm not sure about.
> I was also under the impression that propane and butane burn with a hotter
> flame than alcohol. Any chemists out there care to comment (references
> would be great)?
>
> I know that butane and propane are both hydrocarbon gasses, and I seem
> to remember hearing that butane is lighter than air and propane is
> heavier than air.
I can't resist a question that I know the answer to...
air = 80% N2 + 20% O2 = 28(0.8) + 32(0.2) = 28.8
propane = C3H8 = 44
butane = C4H10 = 58
--> Both butane and propane are heavier than air.
Energy content is a more complicated. As a camper, I would be concerned
with then energy content as a function
of the weight of the thing I carry. Propane can be liquified,
but the tank will be heavier because
Peter Mott
sincl...@hotmail.com
sincl...@hotmail.com
Libor 'Poutnik' Stříž
>>
>> An interesting post Peter, but one question as a layman; Why should the instructions of the co2 detector recommend fixing it onto the ceiling? If butane is heavier than air, should it not be fixed to the wall? It could be of course, badly translated English from the Chinese manufacturer. Appreciate your advice. Rgds Sinclair
>
> I've found the answer; Butane is heavier than air but Co2 is lighter and its Co2 gas that we are detecting. Apparently, Co2 detectors should be fixed on a wall, not the ceiling because heat that stows above will stop detection, and the detector should be 15 feet away from the source of heat. Rgds
>
having about the same molar mass 44 g/mol as propane.
But the point is - at the same temperature.
Hot enough CO2 is lighter/less dense than cold air,
and additionally, there is not only CO2,
but the majority is nitrogen, and also water vapours,
that further decrease the density .
So gases need not to be very hot
to be less dense than normal air at ambient temperature.
The gas from a fire climbs up, not falls down.
--
Poutnik ( The Pilgrim, Der Wanderer )
A wise man guards words he says,
as they say about him more,
than he says about the subject.
ian Gay
> Dne 08/01/2018 v 01:10 sincl...@hotmail.com napsal(a):
>> On Monday, 8 January 2018 00:56:08 UTC+1, sincl...@hotmail.com
>> wrote:
>
>>>
>>> An interesting post Peter, but one question as a layman; Why should
>>> the instructions of the co2 detector recommend fixing it onto the
>>> ceiling? If butane is heavier than air, should it not be fixed to
>>> the wall? It could be of course, badly translated English from the
>>> Chinese manufacturer. Appreciate your advice. Rgds Sinclair
>>
>> I've found the answer; Butane is heavier than air but Co2 is lighter
>> and its Co2 gas that we are detecting. Apparently, Co2 detectors
>> should be fixed on a wall, not the ceiling because heat that stows
>> above will stop detection, and the detector should be 15 feet away
>> from the source of heat. Rgds
>>
> CO2 is heavier/denser then air either,
> having about the same molar mass 44 g/mol as propane.
>
> But the point is - at the same temperature.
>
> Hot enough CO2 is lighter/less dense than cold air,
> and additionally, there is not only CO2,
> but the majority is nitrogen, and also water vapours,
> that further decrease the density .
>
> So gases need not to be very hot
> to be less dense than normal air at ambient temperature.
>
> The gas from a fire climbs up, not falls down.
>
talking about CO detectors. CO is slightly lighter than air, but I
would be surprised if the small difference were significant.
--
*********** To reply by e-mail, make w single in address **************
Libor 'Poutnik' Stříž
>
>>>
>> CO2 is heavier/denser then air either,
>> having about the same molar mass 44 g/mol as propane.
>>
>> But the point is - at the same temperature.
>>
>> Hot enough CO2 is lighter/less dense than cold air,
>> and additionally, there is not only CO2,
>> but the majority is nitrogen, and also water vapours,
>> that further decrease the density .
>>
>> So gases need not to be very hot
>> to be less dense than normal air at ambient temperature.
>>
>> The gas from a fire climbs up, not falls down.
>>
>
> But does anyone actually have CO2 detectors? Maybe the OP is really
> talking about CO detectors. CO is slightly lighter than air, but I
> would be surprised if the small difference were significant.
as the gas burners have oxygen rich combustions.
But CO2 is concern, as burning in small volume as in tents
can significantly increase CO2 content above safe levels.
Having CO2 detector at ceiling
would have mostly fire safety applications in indoors.
For life/health safety it may be better
to be at low levels, to avoid false alarms.
OTOH, CO detector is better to have at ceilings, as it would give
quicker response ( hot gases ).