Absolute alcohol is a common name for the chemical compound ethanol also known as ethyl alcohol. When there is less than one percent water in the ethyl alcohol then it is called as absolute alcohol. In other word the absolute alcohol is at least 99 % pure ethyl alcohol by weight.
Chemical formula:
Physical appearance: Colourless liquid (see the below picture)
Molecular
formula: C2H5OH
Also
Known As: ethanol, ethyl alcohol, pure alcohol, and grain alcohol
It is
the alcohol found in alcoholic beverages.
It is
volatile in nature.
The
ethyl alcohol is also used as a solvents in various chemical reactions.
Methods of preparations of ethyl alcohol -
1) fermentation of sugar
2) The catalytic hydration of ethane
Each method is explained in brief as folloow -
1) fermentation of sugar -
Formarly the main source of ethyl alcohol is fermentation of molasses, however nowadays the catalytic hydration of ethene is used for the manufacture of industrial ethyl alcohol. The ethyl alcohol for use in intoxicating drinks is produced by the fermentation of a sugar: The fermentation of sugar results in the production of ethyl alcohol and carbon dioxide. Yeast is used to cause the fermentation reaction. In the case of sucrose, the fermentation reaction is:
The interesting part is that, the fermentation stops at about the 15% alcohol concentration (by volume), because the Yeast is killed at this concentration of ethyl alcohol. Therefore, the higher concentration of ethyl alcohol are produced by the distillation.
2) The catalytic hydration of ethane -
In this process the ethene and steam (water in the gaseous phase) are passed at about 300°C and a pressure nearly 60 times above atmospheric pressure over a phosphoric acid to produce ethanol. Here a phosphoric acid acts as a catalyst. The chemical reaction is:
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