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/Assets/DisplayAsset.aspx?id=9e8c6eae-6a0e-4b4f-8796-286c47f04a74

http://pubs.acs.org/cgi-bin/abstract.cgi/iecfa7/1964/3/i04/f-pdf/f_i160012a013.pdf?sessid=6006l3

Heat - Latent Heat (http://www.physchem.co.za/Heat/Latent.htm)

Snow Heat Content Equations Formulas Calculator Latent Heat Fusion (http://www.ajdesigner.com/phpsnow/snow_heat_content_equation_latent_heat_fusion.php)

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