A system of units of mass used by druggists in the English-speaking world, before 15ᵗʰ – 19ᵗʰ century. The pound, ounce, and grain of apothecaries' weight are the same sizes as the corresponding units in troy weight, but the scruple and dram are not found in troy weight. The division of the pound into 12 ounces is undoubtedly modeled on the Roman libra, but how the apothecaries' pound got its present value is controversial.
pound |
||||
ounce |
12 |
|||
dram |
8 |
96 |
||
scruple |
3 |
24 |
288 |
|
grain |
20 |
60 |
480 |
5760 |
0.0648 |
1.296 |
3.888 |
31.10 |
0.373 |
By the middle of the 18ᵗʰ century, English druggists were using avoirdupois weight instead of apothecaries' weight, at first to measure what they sold, and then for compounding medicines as well. By the middle of the 19th century apothecaries' weight had largely disappeared. In the United Kingdom the Medical Act of 1858 required the use of avoirdupois weight; the Weights and Measures Act of 1878 retained only the apothecaries' ounce, and that merely permissively.
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Last revised: 8 June 2007.