Environmental impact in 3 numbers

Wouldn’t it be wonderful if the environmental impact of a molecule could be summed up in a few numbers? Such a dream is, of course, impossible, but there is one approach that goes a long way towards this dream. It’s not a new approach, and it is in wide use across a large range of chemical applications, but only recently have the tools become available for it to be applied routinely to a large range of interlocking environmental issues.

Hansen Solubility Parameters (HSP)  can capture a chemical in three numbers that represent the dispersion, polar and hydrogen-bonding aspects of the molecule(*). For those who are interested in more details an excellent summary can be found on Wikipedia: http://en.wikipedia.org/wiki/Hansen_solubility_parameter
Armed with those three numbers you can readily calculate many aspects of a molecule: which solvent is it closest to?; with which polymers is it compatible?; what chemicals will it dissolve?; what is the best blend of solvents to give me the HSP properties of another solvent?; which solvents or chemicals will be likely to go through these gloves or what gloves should I use for protection against a given chemical.

The answer to each of these questions is a number – usually the “distance” between the HSP of two molecules calculated via a simple formula. The value of a solvent blend is simply the weighted average of the (two) solvents in a blend. These calculations can all be done with a spreadsheet if you’ve got a good list of HSP values for solvents and polymers, and if you’ve got a good way to estimate the HSP of a molecule that hasn’t been included in any database.

The recent breakthrough in this technique is the eBook/Software/Dataset package Hansen Solubility Parameters in Practice, or HSPiP, now available on-line at www.hansen-solubility.com. The dataset has everything you need for classic HSP calculations, from large databases of chemicals and polymers, to an automatic method for calculating the HSP of a molecule (from its Smiles or Molfile input) and even an eBook with practical examples showing the technique in practice.

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