Clinical Forensic Medicine

The substance

Of the many types of alcohols, this chapter will discuss only one – ethanol. Ethanol (or ethyl alcohol) is one of a number of alcohols containing a hydroxyl group attached to a carbon atom.

Ethanol is a water-soluble molecule usually produced by the fermentation of fruits and grains by yeast. The process generally stops when the alcohol level reaches about 15% by volume (per cent v/v) because the yeast dies. This produces drinks such as cider, beer and wine. The alcohol content can then be increased by distillation to produce spirits such as whisky, rum or brandy with alcohol contents often between 35% and 45%. The ‘fortified’ wines such as sherry and port have alcohol added to give them strengths between 14% and 22%. One hundred millilitres of a drink with a strength of 10% alcohol will contain 10 ml of alcohol or approximately 10 g (as alcohol is slightly lighter than water the actual weight will be slightly less). In the United States, alcohol strengths are measured in terms of percentage proof with US proof spirit containing 50% of alcohol by volume.

A UK unit of alcohol is 10 ml or 8 g of pure alcohol and is equivalent to half a pint of 3.5% beer, a small (125 ml) glass of wine or a 25 ml pub measure of 40% spirit.