[jubba]

I'm trying to compare the molar heat of ethanol, methanol and propanol using a spirit burner.
Loss of heat isn't a problem because its a qualitative comparision.
but propanol does not completely combust, whilst the others pretty much do.
Is their anything i can do to reduce the effect of this problem or even eliminate it.

Thanks Jubba

[kkjc2]

Try doing it in a calorimeter with Pure oxygen/ air with higher oxygen concentration supplied into the chamber. Use only a small amount of alcohol in that thing, esp when using pure oxygen.

Spirit burner often gives incomplete burning of the larger alcohols, especially if the flame touches the container to be heated, where carbon is deposited as soot. You can also try to heat your water or whatever you are heating with the PrOH flame NOT directly touching it. But that will give you less accurate results, needless to say....

Or you can try to burn just the vapour of these alcohol; so have a small flask of it boiling else where, where the vapour is directed to a glass tube nozzle through insulated tubings(otherwise your vapour condenses back) and ignite the vapour coming from that nozzle to heat your  sample.  However, this is more dangerous, laborious and I am not even sure this will promote complete burning.

The reason it doesn't burn cleanly is that it doesn't get sufficient oxygen to do it; the larger the molecule, the more oxygen you need and complete burning become increasingly difficult.

[mike]

I did a couple of samples yesterday in a ballistic bomb calorimeter. Kerosene, unleaded petrol and peanut oil. I am sure you could probably do alcohols as well.