Proof Spirit system

Ethanol is a central nervous system depressant-it slows the rate at which nerve impulses travel. One or two alcoholic drinks lead to mild sedation. Four or more drinks can cause a loss of coordination and even unconsciousness. Overly excessive drinking—20 shots of a 90-proof spirit in a short time—is lethal. 

Using this proof system, spirits that are 20° overproof, which is the same as saying 120° Sikes or 120 proof, corresponds to a beverage, which contains 68.5% ((120°/175.2°) x 100%) alcohol by volume (Table 16.10). Similarly, spirits that are 70° proof are 70° Sikes or 30° underproof, and will contain ((70°/175.2°) X 100%), or 40% (39.95%) alcohol by volume. 

The density system is used in a number of countries to determine alcohol concentration. The United States uses a simpler proof system based on 100% alcohol being equivalent to 200° proof. Fractions of this concentration, by volume, are specified by multiplying the concentration, in percent by volume, by two (Table 16.10). In France, alcohol concentrations in spirits are simply specified as percent alcohol by volume, sometimes referred to as the Gay-Fussac system. Percent alcohol by weight is used in Germany. 

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