Cool burning Meths

[parsifal]

Well it was just a thought. But easy to prove/disprove, as you suggest.

[lw395]

It seems unlikely that this would affect the burn temperature if it still lights and burns OK.

Allow 20 mls to evaporate in a dish and see if there is water left behind as the alcohol will evaporate before the water. You could speed this up by burning but don't allow the body of liquid to become hot enough to evaporate the water.

Richard

Burning the meths will create water.
I suspect if it's sold as a solvent, it may have either water or something else in it to reduce its volatility and/or its flammability.Ethanol is often about 5% water anyway, the last 5% of water cannot be removed by distillation alone IIRC?

[VicS]

the last 5% of water cannot be removed by distillation alone IIRC?

I could not quote you a % figure* off the top of my head but that's right you cannot get pure anhydrous ethanol by distillation.
It forms an azeotrope .. or constant boiling mixture


*4% .. according to Wiki

[VicS]

Looking at this little further I don't think the MEK content, even if that is present in significant %age will be the cause of the trouble... rather the opposite in fact.

Water content is the most likely cause. Water requires a lot of heat to vaporise it and that heat can only come from burning the ethanol etc. Heat used to evaporate the water in the fuel is heat that is not available to boil the kettle

However if the water content of the new batch is no higher than the water content of the old the question is still unanswered.

The new batch been watered down by an unscrupulous supplier ??

EDIT Some rough calculations suggest that the water theory does not hold water

[2Tizwoz]

To determine how much water there is, weigh some and work out the density.

The alcohol and mek will be around 0.8gm/cc whereas water is 1gm /cc.

[Bosun Higgs]

It seems unlikely that this would affect the burn temperature if it still lights and burns OK.

Yes it will do since the alcohol that is burning will also be boiling off some water in the wick and that takes heat.

Sounds to me as if someone has watered down the meths which should ( apart from the dye and the bitter agent ) be 100% methyl alcohol.

[VicS]

Yes it will do since the alcohol that is burning will also be boiling off some water in the wick and that takes heat.

Sounds to me as if someone has watered down the meths which should ( apart from the dye and the bitter agent ) be 100% methyl alcohol.

No its mostly ethyl alcohol (90%??). Denatured by the addition of an approved denaturing agent and other "ingredients" depending on the exact class of spirit.
There are, I think you may find, also different proof strengths available ... there certainly used to be.

See http://customs.hmrc.gov.uk/channelsP...yType=document
Section16 covers the composition in other EU states

[ngc1]

It seems unlikely that a small proportion of water could be a problem since I have seen posts advocating the addition of up to 10% water to meths in order to overcome the smell produced when meths is burnt. I've not tried it but no mention is made of any decline in heat output if it is done.

[AntarcticPilot]

It seems unlikely that a small proportion of water could be a problem since I have seen posts advocating the addition of up to 10% water to meths in order to overcome the smell produced when meths is burnt. I've not tried it but no mention is made of any decline in heat output if it is done.

There will certainly be an effect from excess water, as the latent of heat of vaporization http://en.wikipedia.org/wiki/Enthalpy_of_vaporizationof water is substantial.

I would suspect that meths sold as a solvent may well have a lower ethanol content than meths sold as a fuel.

[VicS]

There will certainly be an effect from excess water, as the latent of heat of vaporization http://en.wikipedia.org/wiki/Enthalpy_of_vaporizationof water is substantial.

I would suspect that meths sold as a solvent may well have a lower ethanol content than meths sold as a fuel.

Some rough calcs

Molar heat of combustion of ethanol is 327 kcal = 7.1 kcal/g

latent heat of vaporisation of water is 540 cal/g

Take an 80% EtOH 20% H2O mixture

heat produced from burning 1g = 5.68 kcal

The heat required to vaporise 0.2 g water = 108 cal which is not substantial compared with the heat produced by the combustion of the alcohol.

Hence the edit to my earlier post