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Apothecaries' system

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The apothecaries' system was a specialized set of units used to measure mass and volume. It was primarily used by physicians and apothecaries for medical prescriptions. Scientists also utilized this system for their work. It provided the precision necessary for preparing medicinal substances. This system was not just for weight, but also included volume measurements for liquids.

Chambers 1907 p 1172 prescription example
Chambers 1907 p 1172 prescription example

Throughout much of European history, different systems were used for different purposes. This variety helped manage international commerce and specific market needs.

To understand how the system worked, one must look at its subdivisions. The traditional English apothecaries' system was based on the troy pound. This pound was divided into 12 ounces. Each ounce was further divided into 8 drachms. A drachm was split into 3 scruples. Finally, each scruple consisted of 20 grains.

Apothecaries weights 1800
Apothecaries weights 1800

This created a hierarchy of very small units. It allowed pharmacists to measure tiny, exact amounts of medicine. The grain was the smallest standard unit in this sequence.

This system also included a way to measure liquid volume. These units were often called fluid measures. A fluid ounce was a volume approximately equal to an apothecaries' ounce of water. This fluid ounce could be divided into fluid drachms. Sometimes, these were further divided into fluid scruples.

Apothecaries weights 1800
Apothecaries weights 1800

The smallest unit for liquids was traditionally called a drop, or "gutta" in Latin. However, a drop was not a standardized volume. It was measured by releasing liquid from the lip of a vial. The 1809 London Pharmacopoeia introduced new terms like "minim" to help standardize these liquid measurements.

The history of these units reaches back to antiquity. The apothecaries' system was a subset of the Roman weight system. It was inherited through influential medical treatises. These writings were produced by Greek physicians such as Dioscorides and Galen. They lived during the 1st and 2nd centuries.

DBP 1991 1490-R
DBP 1991 1490-R

Their work helped preserve these measurement standards for centuries. This historical connection ensured that medical professionals across Europe used similar logic for dosing.

In the 19th century, many regions faced confusion due to overlapping systems. Most European cities used a "commercial" or "civil" system for general trade. An example is the English avoirdupois system. However, they used a second system, like the troy system, for precious metals. The apothecaries' system was closely related to the troy system. For example, the pound and grain were exactly the same in both.

Apothecaries weights 1800
Apothecaries weights 1800

This often led to confusion when apothecaries bought goods in one system and sold them in another.

Several attempts were made to unify these different standards. In 1850, an innovation was proposed in Ireland. The Irish College suggested replacing the troy pound with the avoirdupois pound. They wanted to align the units used for sales with the units used for purchases. This proposed system used 16 ounces per pound. It would have changed the value of the drachm significantly.

Apothecaries weights 1800
Apothecaries weights 1800

While this specific Irish proposal was not widely adopted, it showed the growing need for standardization.

Legislative changes eventually led to the system's decline. The British Medical Act of 1858 was a radical step. It prescribed the use of the avoirdupois system for the United Kingdom. This included the use of the imperial avoirdupois pound, which contained 7,000 grains. The traditional subdivisions like the drachm and scruple were eventually discontinued in official pharmacopoeias.

Apothecaries weights 1800
Apothecaries weights 1800

This move helped simplify the complex web of different weights used in pharmacy.

The system eventually became obsolete in many parts of the world. In the United Kingdom, the Weights and Measures Act 1976 restricted its use. It could then only be used for precious metals and stones. In both the United Kingdom and the United States, the metric system became mandatory. This change occurred in 1971.

DBP 1991 1490-R
DBP 1991 1490-R

Today, the metric system provides a universal standard for science and medicine worldwide.

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File:DBP 1991 1490-R.JPG
DBP 1991 1490-R.JPG
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Chambers 1907 p 1172 prescription example.png
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Apothecaries weights 1800.png
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