Apothecaries’ Pound

The nominal top of the apothecaries’ scale, at twelve ounces or 5,760 grains, and identical in weight to the troy pound.

The apothecaries’ pound existed mainly to complete the system. Medicines were compounded in ounces, drachms, scruples and grains, and a pound of anything was a bulk quantity a dispensing chemist would rarely reach for, so the unit sat at the head of a scale whose real work happened four rungs below it. It shares its weight exactly with the troy pound, both being twelve ounces of 480 grains, which meant a chemist buying raw materials from a merchant who reckoned in troy weight could do so without conversion. That shared foundation runs all the way down: avoirdupois, troy and apothecaries’ weights all agree at the grain and diverge immediately above it.