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Units of measure. The word “scruple” has been used in these pages but it’s not a word we use today. It is in fact a unity of measurement.

  • There are eight drachms to the ounce
  • and three scruples to the drachm
  • and 20 grains to the scruple.
  • one Troy ounce is equal to 31.1 grammes, not quite the same as one ounce avoirdupois, which is 28.35 grammes.

Apothecaries’ system

The apothecaries’ system of weights is a historical system of mass units that were used by physicians and apothecaries for medical recipes, and also sometimes by scientists.

The English version of the system is closely related with the English troy system of weights, the pound and grain being exactly the same in both.

It divides a pound into 12 ounces, an ounce into 8 drachms, and a drachm into 3 scruples or 60 grains.

This exact form of the system was used in the United Kingdom; in some of its former colonies it survived well into the 20th century. The apothecaries’ system of measures is a similar system of volume units based on the fluid ounce. For a long time, medical recipes were written in Latin, often using special symbols to denote weights and measures.

Weights: UK (Imperial) and US
Weight
(abbreviation)
pound
(℔)
ounce
(℥)
dra(ch)m
(ʒ)
scruple
(℈)
grain
(gr.)
1 ℔ 12 ℥ 96 ʒ 288 ℈ 5,760 gr.
1 ℥ 8 ʒ 24 ℈ 480 gr.
1 ʒ 3 ℈ 60 gr.
1 ℈ 20 gr.
metric equivalent 373 g 31.1 g 3.89 g 1.296 g 64.8 mg
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