Well it was just a thought. But easy to prove/disprove, as you suggest.
Results 11 to 20 of 21
Thread: Cool burning Meths
04-05-12, 14:57 #11"Our business in life is not to succeed but to continue to fail in good spirits." RLS
04-05-12, 16:14 #12Registered User
- Join Date
- May 2007
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?
04-05-12, 17:16 #13the last 5% of water cannot be removed by distillation alone IIRC?
It forms an azeotrope .. or constant boiling mixture
*4% .. according to Wiki
Last edited by VicS; 04-05-12 at 17:19.
04-05-12, 23:53 #14
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
Last edited by VicS; 05-05-12 at 11:20.
05-05-12, 09:13 #15
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.
05-05-12, 14:58 #16
05-05-12, 15:04 #17
There are, I think you may find, also different proof strengths available ... there certainly used to be.
Section16 covers the composition in other EU states
Last edited by VicS; 05-05-12 at 15:11.
05-05-12, 16:06 #18Registered User
- Join Date
- May 2010
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.
05-05-12, 19:21 #19
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.
05-05-12, 21:06 #20
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