How do I calculate latent heat of vaporisation of an industrial solvent like methanol, toulene,pyridine etc...

You might want to check out the following links:

http://www.studyloft.com/Admin/Asset...6-286c47f04a74

http://pubs.acs.org/cgi-bin/abstract...?sessid=6006l3

Heat - Latent Heat

Snow Heat Content Equations Formulas Calculator Latent Heat Fusion

I hope that they are helpful. Just did a little searching for you. In over my head on this one.