Alcohol and water form the basis of every spirit and also play a central role in whisky.
Whisky consists mainly of water and alcohol. The rest (<1%) in whisky are flavourings and aromas. When we talk about alcohol, we are referring exclusively to ethyl alcohol, which is also abbreviated to ethanol. The chemical formula is C2H5OH.
In whisky production, special care is taken to ensure that no methyl alcohol (methanol, CH3OH) is contained in the finished product. The yeasts used are bred in such a way that they do not produce methanol. The separation of the foreshot during distillation ensures double safety.
Now it's getting chemical!
The left-hand molecule in the right-hand diagram represents the ethanol molecule. The grey atoms are the carbon atoms (C), the red atom is the oxygen (O) and the white-grey atoms represent the hydrogen (H). To the right of the ethanol molecule is a water molecule (H2O).
A closer look at the ethanol molecule reveals that, apart from the oxygen atom, the molecule is symmetrical to a vertical plane between the carbon atoms. Only one hydrogen atom is replaced by an oxygen/hydrogen group (a so-called OH group). This OH group causes the ethanol molecule, which is electrically neutral overall, to exhibit local electronegativity differences (so-called dipoles d+, d-). Normal water molecules also show these dipoles, as they are also arranged at an angle (angle 109°). These dipoles on the ethanol and water side now ensure that hydrogen bonds are formed between the molecules.
For this reason, the OH group is hydrophilic (water-loving). The rest of the ethanol, the C2H5 group, is lipophilic (fat-loving). Of course, the formation of hydrogen bonds is comprehensive, so that dipoles with reversed signs also attach to all the dipoles in the drawing above. In individual cases, these can be dipoles of water or alcohol molecules.
Whisky and Water - Background Knowledge
Do you always drink your whisky neat or do you dilute it with water? If you belong to the second group, this video gives you background knowledge in physics and chemistry. In another video, it's all about the taste experience.
Questions and answers
Here you will find concise answers to the most important questions about alcohol and water in whisky.
Why does high-proof whisky get warm when you dilute it with water?
The OH groups of the ethanol form hydrogen bonds with the water molecules and this creates a heat of mixing that noticeably heats the mixture.
Why do some whiskies become cloudy when diluted with water?
Whisky contains ethanol-soluble components that are poorly soluble in water. If the water content is increased, it takes a certain amount of time for these components to reattach to the alcohol (lipophilic) and the whisky becomes clear again.
Why are individual whiskies chilled before filtering?
Most chemical substances are more soluble at higher temperatures than at lower ones. The cloudy substances come out of the barrel wall into the whisky during storage. If the whisky is now cooled, these cloudy substances precipitate and can be better absorbed by a filter.
Why do streaks form when you mix whisky with water?
This is not a chemical but rather a physical effect. The difference in density between water and alcohol, combined with different refractive indices, leads to the formation of streaks. Once the water and alcohol have mixed properly, you will no longer see any streaks.
Why can't 100% ethanol be produced by distillation?
Ethanol and water form an azeotrope (96% ethanol, 4% water) whose boiling point is below the boiling point of pure ethanol (78.15°C at 1 bar (760mm) and 95.6% alcohol content (weight)). When boiling an ethanol-water azeotrope, the boiling point of 100% ethanol can therefore never be reached, as the 96/4 mixture boils first. With the addition of benzene (caution: toxic), 100% ethanol can be produced, as the benzene forms an azeotrope with the water and can thus transport the water. Nowadays, it is healthier to use molecular sieves, which can be used to produce almost 100% ethanol.
Some Physical Data
| Alcohol- concentration | Density (20°C, kg/l) | Refractive index to air (20°C, sodium light) | Relative viscosity to water (20°C) |
|---|---|---|---|
| 0% 1) | 0.9982 | 1.3333 | 1.000 |
| 10% | 0.9819 | 1.3395 | 1.498 |
| 20% | 0.9687 | 1.3469 | 2.138 |
| 30% | 0.9539 | 1.3535 | 2.662 |
| 40% | 0.9352 | 1.3583 | 2.840 |
| 46% | 0.9227 | 1.3604 | 2.837 |
| 50% | 0.9139 | 1.3616 | 2.807 |
| 60% | 0.8911 | 1.3638 | 2.542 |
| 70% | 0.8676 | 1.3652 | 2.210 |
| 80% | 0.8436 | 1.3658 | 1.877 |
| 90% | 0.8180 | 1.3650 | 1.539 |
| 100% 2) | 0.7893 | 1.3614 | 1.201 |
1) Pure water
2) Pure alcohol
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Conclusion
The interaction of alcohol and water is a decisive factor for the quality, drinking strength and flavour perception of whisky. If you understand these relationships, you can compare bottlings more specifically and control your own taste more consciously - whether neat, with water or when selecting different alcohol strengths Discover whiskies with different characters and find your personal favourite.
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