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I have a bowl containing cheap wine and an immersible fish tank heater. The heater warms the wine to 30 deg C. The bowl is located in a large closed bucket, where it sits on a support. The bucket is sited out of doors in winter when the air temperature is Ca 1 deg C. Evaporation occurs and the vapour condenses on the inner surface of the bucket. Droplets of condensate run down and form a pool of liquid on the floor of the bucket.

Question: what can be predicted about the composition of the condensate?

Question #2 What effect is achieved by raising or lowering the temperature of the wine on the composition of the condensate. In plain language what temperature of the wine will give me the highest concentration of alcohol in the condensate? How can the strength of the alcohol be measured?

Question #3 What is the effect of different air temperatures outside of the bucket (on the composition of the condensate)?

Question #4 Why is this method not commonly used to concentrate alcohol?

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Yes you can do that, this technique is called 'distillation' (it requires a minimum difference of 10 degrees celsius to seperate two liquids with different boiling points, for efficiency), I don't know what temeperature the fish tank heater runs at, but you should know that ethanol i,e. what you are trying to separate evaporates at 37 degrees celsius same as normal body temperature, and the temperature of the cooling plate should be < 27 degrees for efficiency

Edit -
yes, exactly the boiling point of ethanol is 78.3 degrees but ethanol is highly volatile and evaporates very fast at 37 degrees (without taking much water vapour with it) as far as my observation is concerned(with room temperature around, 1 atm pressure). the values I mentioned are the optimal conditions with experimental background. your goal as I can percieve is to avoid as much water as possible, if you take the condenser temperature to below 10 degrees the water vapour present in air will also start to condense at a good rate

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  • $\begingroup$ I have set the fish tank heater to 30 deg C, but I could set it as low as 20 deg C. How would the lower temperature affect the composition of the condensate? The "cooling plate" (the walls of the bucket) are at, or close to, the external air temp which is currently 1 deg C. So there is a 29 degree difference between the wine and the condensing surface. If the weather gets colder (the differential increases) how does this affect the condensate? $\endgroup$ Dec 4 '14 at 15:29
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    $\begingroup$ << ethanol . . . evaporates at 37 degrees celsius>> My understanding is that ethanol boils at 78.3 C. but I am concerned with evaporation, which I think can occur at any temperature above the solid state (frozen ethanol) not solely at the 37 degrees you mention. The point of my question is to see if different conditions can improve the process in the aim of achieving a higher ABV. $\endgroup$ Dec 4 '14 at 15:40
  • $\begingroup$ This doesn't really answer the question at all. Can you elaborate as to the other aspects of the questions the OP asked? $\endgroup$
    – jonsca
    Dec 4 '14 at 23:26
  • $\begingroup$ 37 degrees celsius is a temperature for efficiency under room temperature i.e, 25 degrees. I have myself experienced the values experimentally in lab $\endgroup$
    – user10153
    Dec 5 '14 at 5:52
  • $\begingroup$ the temperature difference mentioned by the questioner should also work efficiently, the only problem here is that if the setup is open to air it might condense water from air as well. $\endgroup$
    – user10153
    Dec 5 '14 at 5:56
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The answer to my principal question is that you can concentrate an aqueous ethanol solution by "room temperature distillation". I don't have the right equipment to be able to determine what variation in output quantity and strength might be obtained by varying the temperature of the source solution and the condenser surface. But I can state that the alcohol concentration in the condensate under the conditions I used finally was ca 18% coming from the source solution which was 11%. What I like about the process is that little energy is used for heating(30 watts) and no water is wasted for cooling as in conventional distillation. Further experiment - from a wash of sugar and beer yeast using the method above I obtained a distillate which measured 36% on my $3 Russian alcohol hygrometer.

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  • $\begingroup$ When you say "little energy is used" what you mean is that the rate of energy use is low. Given that the low temperature distillation will take a lot longer, I don't think you can comfortably say the total use is lower. $\endgroup$
    – matt_black
    Dec 21 '14 at 21:59

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