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Wren

Contents of gas bubbles during louche?

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Just thought that I would pose a simple-minded question regarding some of the chemistry that occurs during the formation of the louche: what gases are produced (= tiny bubble formation) when water is slowly added to absinthe?

 

I have been curious about this for a while. Thanks in advance for any information!

 

:cheers:

Edited by Wren

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Drop water into water, alcohol into alcohol, oil into oil or any combination of the aforementioned and bubbles will form. It's just the dynamics of liquid. Just like how sea water turns frothy when waves crest.

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It's interesting that you mention that because I have tried to assuage my curiosity about this by slowly dripping cold water into other (non-alcoholic) beverages, and I haven't noticed the same effect. I tend to go with a very slow (10-20 min) fountain drip when I am preparing a glass of absinthe, and I often notice a considerable number of bubbles that form on the bottom of the glass (as well as the sides), which rise to the top. Sometimes the bubble action almost reminds me of sparkling water (okay, not quite).

 

Thanks again!

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I assume what you are seeing is simply air coming out of solution. The sparkling water bubbles are CO2 bubbles coming out of solution.

 

I could be very wrong though.

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I've seen the same thing but never thought anything of it.

 

A friend of mine got me a bottle of rectified spirit (+95% abv.) from Poland. I added water to about 100ml of it and it started to fizz, bubbled up, and turned kind of cloudy, almost like there was a drop of milk in there. After an hour or so it was clear and still again, but I was worried it was going to eat through the plastic for a moment.

 

I know that the alcohol content is so high it actually 'sucks' the moisture out of the air, so maybe the bubbles produced by that and absinthe are due to the high alcohol 'attracting' the water that we put into the glass. There are also always bubbles that are produced because air gets into the liquid when it is disturbed by the drops of water, as we all already know.

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An educated guess:

 

It's possible that some of the oils that precipitate out of the alcohol act as surfactants, which lower surface tension and inhibit bubble coalescense.

 

When one liquid is dripped into another, microfine air bubbles are introduced from the turbulence at the surface. In a 'clean' liquid, these bubbles coalescense into larger ones and immediately rise to the surface. When surfactants or electrolytes are present, coalescense is inhibited and small bubbles tend to remain in the liquid. These small bubbles will also tend to adhere to the inside of the glass.

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"When alcohol and water are mixed together the resulting liquid occupies, after agitation, a less volume than the sum of the two original liquids. This contraction is greatest when the mixture is made in the proportions of 52.3 volumes of alcohol and 47.7 volumes of water, the result being, instead of 100 volumes, 96.35. A careful examination of the liquid when it is being agitated reveals a vast number of minute air-bubbles, which are discharged from every point of the mixture. This is due to the fact that gases which are held in solution by the alcohol and water separately are less soluble when the two are brought together; and the contraction describe above is the natural result of the disengagement of the such dissolved gases."

 

-F.B. Wright "Distillation of Alcohol & De-naturing" 1906

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