Propane and butane...

[Dallas Dave]

What is the best gas - propane or butane - for explosive and stuff and why?

Is a butane/propane mix in ration 70:30 a good mixture?

What is the most viable:

10 litres of petroleum spirits @ £55

OR

10 litres of a butane/propane mix in ration 70:30 @ £95?

Thanks.


P.S. Could you send us some good links about gas explosions and FAEs and stuff so I odn't have to keep bothering you guys? Cheers

(You could try searching the forum for some 'good links' to FAE data - kingspaz)

[kingspaz]

I'd imagine propane alone would be a better fuel as it tends to burn to completion better than butane. Also, are you talking about fast delfagration of the fuel air mix, or detonation. For both I'd imagine propane would be better.

I'd guess the reaction of combusting a propane molecule would be faster than the reaction of combusting a butane molecule since the propane is smaller so there is 'less to do'.

I'd guess again the propane would be better than butane for a detonation reaction since propane reacts faster...

All this could be bullshit since my reasoning is most likely flawed, would an actual chemist like to agree/disagree?

[The Anarch]

Butane will give more heat output, but that doesn't really matter. Kingspaz is right, propane is better as it has a smaller molecule and reacts faster.

[xyz]

It all depends on how much confinement you can give it.

For most situations propane will be better, but if you are able to use heavy confinement then butane will be better (higher heat output and higher pressures). You just need sufficient confinement to allow enough of it to react.

SWIM makes gas salutes using 2L and 3L soft drink bottles wrapped in string and filled with a stoichiometric mixture of butane and oxygen which seems to work quite nicely. Please note however that the reason for using butane in this situation is that it is much easier to liquefy than propane (SWIM uses a syringe to measure out liquid butane), nothing to do with it working better or anything.

If anyone wants the full process on making these bottle salutes and calculating how much liquid butane to add, then I'll post it later. The same process can be used to calculate for liquid propane as well, if you have the info on how much it expands upon evaporation at room temperature.

[Anthony]

You guys are feeling very tolerant today!

So, what application exactly is described by: "explosive and stuff"?

If you want help, you've got to help yourself first. That includes using search engines, such as the one included on this site, and google.

What is "petroleum spirits"? That could be any of several dozen petroleum products. I can't guess by the price, because I can't think of anything that costs that damn much, even off the shelf in tiny quantities. Petrol costs £0.80/litre, your stuff costs £5.50/litre.

10l of propane/butane costs £95? Liquified gases are sold by weight, not volume! 10l at what pressure? Again, the fucking price - 10kg of propane or butane is less than £15 from Calor.

Propane and butane have nearly identical calorific values. The main difference is their boiling point: propane -42*C, butane 0.6*C. So butane would be useless during the winter. The gases are mainly mixed to give a required vapour pressure.

[zeocrash]

Theoretically there would be the most energy in the petrolium spirit., Mainly as it has larger molecules, though it would not burn as fast.
I'm assuming you're talking about 10l or liquid butane/propane rather than gaseous, because 10L of gasseous propane is fuck all.

[Dallas Dave]

Yes 10l of liquid.

The liquid I looked at used litres so I'll just go by that.