Why is it 72 dynes?

Really the surface tension of water is 72 dynes?  Yes.  As the name of this blog suggests it is only 72 dynes.  However, according to a study by Angus Gray-Weale and colleagues this could be even larger depending on the attraction between hydroxide dipoles but is reduced by a 'layer of hydroxide-enriched water extends up to a nanometre'.  The results are controversial but interesting as they still try to understand surface tension at different levels.  Still more understanding is needed on both macroscopic and microscopic levels to understand what is happening at the air-water interface.  For a summary of the article it is here:

 
http://www.rsc.org/chemistryworld/2012/08/getting-under-skin-water

References

1. M Liu, J K. Beattie and A Gray-Weale, J. Phys. Chem. B, 2012, 116, 8981 (DOI: 10.1021/jp211810v)