Tuesday, March 04, 2008

Absinthe: Part 1

As I type this, I can't recall a particular quotation by Lovecraft on absinthe, but as a chemist this is too neat not to blog. I foud it in today's Courier-Journal (Louisville) p. E3 extracted from langmuir of the American Chemical Society - a journal of surface physical-chemistry.

A unique characteristic of absinthe (shared by other oil containing liqueres such as pernod and ouzo) is that it turns cloudy upon addition of water. Excess water alters the oil-alcohol-water balance and causes the oil particles to pop out of solution and thus defracting light. Once out of solution, the particles of oil begin to gradualy coalesce over a period of weeks and that oil rises to the top of the solution.

The plant oils are usually soluble in at least 45% alcohol.

Theoretical calculations by a team of Dutch chemists led by Erik van der Linden of Wageningen University explored the physics of this phenomenon and showed that the more watery the mixture, supposedly the longer the drink remained cloudy. That's because it should be harder for the oil molecules to coalesce into large droplets and therefore the longer it will take for the oil to “cream out” on the surface.

The Dutch experiments, however, showed just the opposite.

The more alcoholic the mixture, the longer the cloudiness lasted and the slower the creaming.
What is known about molecular activity at the interface of oil droplets and water, the solubility of oil in the mixture and the density issues involved is “not sufficient to explain the results for these unique three-component systems,” the authors write.

Three component systems are hard to predict since not all molecular forces are easily estimated.

Lovecraft, as a chemist, would have appreciated the experiment.

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