On 01/07/2007 08:23, Weatherlawyer wrote:

All paraffins aka alkanes are heavier than air.

density of air ~1.3kg/m^3

They run from Methane at 4 carbon atoms

A single Carbon atom with 4 Hydrogen atoms around it
density ~0.7kg/m^3

through to Octane with ten,

A chain of 8 Carbon atoms with 18 Hydrogen atoms strung along them.
volatile liquid but for once you're right, the vapour density /is/
heavier than air at ~5.2kg/m^3 hence the vapour recovery being
introduced at petrol stations.