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Alcohol and Water
Questions and Answers
Whisky consists primarily of water and alcohol. Other constituents (usually < 1%) in the whisky are taste materials and flavours, called "congeners". When refering to alcohol, we mean ethyl alcohol, also known as ethanol. The chemical formula is C2H5OH.
The process of whisky production ensures that no methyl alcohol (methanol, CH3OH) is present in the finished product. The yeast employed in the conversion of sugars to alcohol have been selectively developed in such a way as to minimize or eliminate the production of methanol. During distillation, the removal of the foreshots and feints, and the collection of only the "middle cut" provides further assurance.
The molecular model in the upper left diagram represents the ethanol molecule. The gray atoms are carbon atoms (C), the red atom is the oxygen (O) and the white-gray atoms represent hydrogen (H). A model of the water molecule (H2O) is shown to the right.
A closer examination of the spatial properties of the ethanol molecule shows that the molecule without the oxygen atom is symmetrical with respect to the perpendicular plane through the carbon atoms. To form ethanol, only a hydrogen atom has been replaced by an oxygen-hydrogen group (the OH group). The ethanol molecule is electrically neutral in total but has local separation of electrical charge (so-called dipoles d+, d-). This is due to the differing affinity for electrons by oxygen and the hydrogen atom attached to it. The oxygen attracts electrons, thus developing a slightly negative charge, whilst the hydrogen atom suffers an equivalent deficiency of charge, and is therefore slightly positive. Water molecules also exhibit these dipoles, since they also are non-linearly arranged (angle 109 deg). Because opposite charges attract, dipoles on the ethanol and water molecules allow the formation of weak hydrogen bonds between negative and positive charges on the different molecules.
The OH group on the ethanol is said to be hydrophilic (water-loving).The remainder of ethanol, the C2H5-group, is said to be hydrophobic(water-hating) or lipophilic (fat-loving). Naturally the formation ofthe hydrogen bonds is global, so that all dipoles of all the molecules,as illustrated on the drawing above, establish such bonds. Inconsequence, ethanol and water are able to mix in all proportions (theyare completely miscible).
Questions and Answers
Why does high proof whisky become warm when diluted with water?
Why do some whiskys show cloudiness when diluted with water?
Why are some whiskys cooled down and then filtered prior to
Why do streaks form if whisky is mixed with water?
Why is it not possible to produce 100% ethanol by simple
This can be overcome by altering the azeotropic mixture so that it's boiling point is higher than that of pure alcohol. This then allows the ethanol to be distilled off. Industrially, many different chemicals have been used to form an azeotrope with water, including benzene (C6H6), which is both poisonous and carcinogenic. Modern techniques, such as the use of molecular sieves are healthier, and permit the production of almost 100% pure ethanol.
Some physically data
1) Pure water
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