[glovesforfoxes (OP)]

Some of you may know, or none of you may know, that I'm currently studying Chemistry at first year degree level. As part of our course we are required to perform practicals, and one of the rotations is an organic rotation. In this, we are required to heat a substance under reflux in a round bottomed flask, say 100ml. I have noticed that if I move the microbunsen so that the top of it is almost touching the bottom of the flask, the flame seems to spread out in a small circle and there is a small visible gap of a millimetre or less between the flame and the bottom of the flask. Can anyone explain where this gap comes from? Is there an air pocket trapped, or is it my faulty perception, or something else?

Edit: I just realised this might be more appropriate in the physics section. Sorry mods if you agree! [:I]

[glovesforfoxes (OP)]

Thanks - I don't have access to white hot iron, but I'll try boiling some water on a blue flame and then changing to an orange flame to see if there is any difference.