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Historical system of mass and volume units used by physicians and apothecaries

The apothecaries' system, or apothecaries' weights and measures, is a historical system of mass and volume units that were used by physicians and apothecaries for medical prescriptions and also sometimes by scientists. The English version of the system is closely related to 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 of 20 grains each. 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. The use of different measure and weight systems depending on the purpose was an almost universal phenomenon in Europe between the decline of the Roman Empire and metrication. This was connected with international commerce, especially with the need to use the standards of the target market and to compensate for a common weighing practice that caused a difference between actual and nominal weight. In the 19th century, most European countries or cities still had at least a "commercial" or "civil" system (such as the English avoirdupois system) for general trading, and a second system (such as the troy system) for precious metals such as gold and silver. The system for precious metals was usually divided in a different way from the commercial system, often using special units such as the carat. More significantly, it was often based on different weight standards. The apothecaries' system often used the same ounces as the precious metals system, although even then the number of ounces in a pound could be different. The apothecaries' pound was divided into its own special units, which were inherited (via influential treatises of Greek physicians such as Dioscorides and Galen, 1st and 2nd century) from the general purpose weight system of the Romans. Where the apothecaries' weights and the normal commercial weights were different, it was not always clear which of the two systems was used in trade between merchants and apothecaries, or by which system apothecaries weighed medicine when they actually sold it. In old merchants' handbooks, the former system is sometimes referred to as the pharmaceutical system and distinguished from the apothecaries' system. TOC

Until around 1900, medical prescriptions and most European pharmacopoeias were written in Latin. Here is a typical example from the middle of the 19th century. Infusion of Dandelion, &c. RxInfusi Taraxaci, f℥iv. 4 fluid ounces of dandelion infusion Extracti Taraxaci, fʒij. 2 fluid drachms of dandelion extract Sodæ Carbonatis, ʒss. 1/2 drachm of sodium carbonate Potassæ Tartratis, ʒiij. 3 drachms of potassium tartrate Tincturæ Rhei, fʒiij. 3 fluid drachms of rhubarb tincture ———— Hyoscyami, gtt. xx. 20 drops of henbane tinctureFiat Mistura. Signa.—One third part to be takenthree times a day. In dropsical and visceral affections. Make mixture. Write: "One third part to be takenthree times a day. In dropsical and visceral affections." The use of Latin ensured that the prescriptions could be read by an international audience. There was a technical reason why 3 ʒ was written ʒiij, and 1/2 ʒ as ʒss: Writing iii as iij would prevent tampering with or misinterpretation of a number after it is written. The letters "ss" are an abbreviation for the Latin "semis" meaning "half", which were sometimes written with a ß. In Apothecaries' Latin, numbers were generally written in Roman numerals, immediately following the symbol. Since only the units of the apothecaries' system were used in this way, this made it clear that the civil weight system was not meant.

Empress Maria Theresia of Austria reformed the measures and weights of the Habsburg monarchy in 1761. From 1803 to 1815, all German regions west of the River Rhine were French, organised in the départements Roer, Sarre, Rhin et Moselle, and Mont Tonnerre. As a result of the Congress of Vienna these became part of various German states. A large part of the Palatinate fell to Bavaria, but having the metric system it was excepted from the Bavarian reform of weights and measures.

+ Apothecaries' weight in Prussia 1 ounce Standard 1 pound 29.82 g Nuremberg (initially) 357.8 g 29.23 g Civil pound (from 1816) 350.8 g 31.25 g Metric pound (from 1856) 375.0 g Abolished Metric pound (from 1867) Abolished

In Prussia, a reform in 1816 defined the Prussian civil pound in terms of the Prussian foot and distilled water. It also redefined the apothecaries' pound as 12 ounces, i. e. of the civil pound: 350.78 g. This reform was not popular with apothecaries, because it broke the uniformity of the apothecaries' pound in Germany at a time when a German national state was beginning to form. It seems that many apothecaries did not follow this reduction by 2%. Another reform in 1856 increased the civil pound from 467.711 g to 500.000 g (the German civil pound defined by the Zollverein), as a first step towards metrication. As a consequence the official apothecaries' pound was now 375.000 g, i. e. it was increased by 7%, and it was now very close to the troy standards. §4 of the law that introduced this reform said: "Further, a pharmaceutical weight deviating from the civil weight does not take place." But this paragraph was suspended until further notice. The abolishment of the apothecaries' system meant that doctors' prescriptions had to take place in terms of the current civil weight: grammes and kilograms. This was considered unfeasible by many, and the state received numerous protests and asked for expertises. Nevertheless, by 1868 §4 of the earlier reform was finally put into force.

Britain was initially involved in the development of the metric system, and the US was among the 17 initial signatories of the Metre Convention in 1875. Yet in spite of enthusiastic support for the new system by intellectuals such as Charles Dickens, these two countries were particularly slow to implement it. In the US, the metric system replaced the apothecaries' system in the United States Pharmacopeia of 1971. In the UK, metric drug measurements were required for dealings in drugs from January 1, 1971.