Apothecaries’ unit is a term that refers to a system of weights and measures that was used by physicians and apothecaries for medical prescriptions and sometimes by scientists. It is a historical system that originated from the Roman and Greek weight systems and was widely used in Europe until the 19th century. In this article, we will explore the origin, units, and usage of the apothecaries’ unit system.

The apothecaries’ unit system is based on the grain, scruple, dram, ounce, and pound units that were inherited from the Roman weight system. The grain (Latin: granum) was the smallest unit and was derived from the weight of a barley or wheat seed. The scruple (Latin: scrupulum) was equivalent to 20 or 24 grains, depending on the region. The dram (Latin: drachma) was equivalent to 3 scruples or 60 grains. The ounce (Latin: uncia) was equivalent to 8 drams or 480 grains. The pound (Latin: libra) was equivalent to 12 ounces or 5760 grains.

The apothecaries’ unit system also incorporated the drachm unit from the Greek weight system. The drachm (Greek: δραχμή) was a silver coin that weighed about 4.3 grams and was used as a standard of exchange in ancient Greece. The drachm was equivalent to 3 scruples or 60 grains in the apothecaries’ unit system.

The table below shows the units of the apothecaries’ unit system and their symbols, values, and conversions to other systems.

| Unit | Symbol | Value | Metric Equivalent | Avoirdupois Equivalent |
|——|——–|——-|——————-|————————|
| Grain | gr | 1/5760 lb | 64.79891 mg | 1/7000 lb |
| Scruple | ℈ | 20 gr | 1.295978 g | 0.002286 lb |
| Dram | ℨ | 3 ℈ or 60 gr | 3.887935 g | 0.006857 lb |
| Ounce | ℥ | 8 ℨ or 480 gr | 31.10348 g | 0.054857 lb |
| Pound | ℔ | 12 ℥ or 5760 gr | 373.2417 g | 0.822857 lb |

The apothecaries’ unit system also used some volume units based on the fluid ounce (fl oz). The fluid ounce was defined as the volume of one ounce of water at a specified temperature and pressure. The fluid ounce was equivalent to about 29.57 mL in the metric system and about 1.041 fl oz in the avoirdupois system.

The table below shows some of the volume units of the apothecaries’ unit system and their symbols, values, and conversions to other systems.

| Unit | Symbol | Value | Metric Equivalent | Avoirdupois Equivalent |
|——|——–|——-|——————-|————————|
| Minim | ♏︎ | 1/60 fl oz | 0.061611 mL | 0.002083 fl oz |
| Fluid dram | ♏︎ℨ or fℨ | 60 ♏︎ or 1/8 fl oz | 3.696691 mL | 0.125 fl oz |
| Fluid ounce | ♏︎℥ or f℥ | 8 ♏︎ℨ or fℨ or 1 fl oz | 29.57353 mL | 1 fl oz |
| Pint | O or pt | 16 ♏︎℥ or f℥ or fl oz | 473.1765 mL | 16 fl oz |
| Gallon | C or gal | 8 O or pt or 128 ♏︎℥ or f℥ or fl oz |3785.412 mL|128 fl oz|

The apoth