Apothecaries' system
Historical medical weight and volume system used by apothecaries.
The apothecaries' system is a historical system of mass and volume units used by physicians and apothecaries for medical prescriptions, and sometimes by scientists. It is closely related to the English troy system, with the pound and grain identical in both, dividing a pound into 12 ounces, an ounce into 8 drachms, and a drachm into 3 scruples of 20 grains each. This system was used in the United Kingdom and survived in some former colonies into the 20th century, with medical recipes often written in Latin using special symbols.
- field
- Historical weights and measures
- known_for
- System of mass and volume units for medical prescriptions
- related_system
- English troy system
- key_units
- Pound (12 ounces), ounce (8 drachms), drachm (3 scruples), scruple (20 grains)
Lore & Background
The apothecaries' system inherited its special units from the general-purpose weight system of the Romans, via influential treatises of Greek physicians such as Dioscorides and Galen. The English version used the troy pound and grain, but the pound was divided into 12 ounces, unlike the commercial avoirdupois system. In some regions, the apothecaries' weights and commercial weights differed, leading to uncertainty in trade between merchants and apothecaries. This was not widely adopted.
Reader's Guide
The apothecaries' system represents a key example of the historical fragmentation of measurement systems in Europe, where different systems coexisted for commerce, precious metals, and medicine. Its significance lies in its long use for medical prescriptions, influencing pharmacopœias and medical practice for centuries. The system's gradual replacement by the avoirdupois and later metric systems reflects broader trends toward standardization in the 19th and 20th centuries. The Irish and British attempts to reform the system highlight the practical challenges of unifying weights used by apothecaries for purchase and sale. The system's legacy persists in the continued use of troy weights for precious metals and in the distinct US and UK fluid ounce systems derived from apothecaries' volume measures.
Did You Know?
- The apothecaries' pound and grain were identical to the troy pound and grain.
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