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."Medicinal-Gewicht, Apotheker-Gewicht ist dasjenige Gewicht, nach welchem Aerzte und Apotheker die Quantitäten der Arzneimittel bestimmen. Nur an wenigen Orten werden beide Arten der Gewichte unterschieden und Medicinalgewicht bei dem Einkauf der Arzneiwaaren im Großen von dem Apothekergewicht bei der Anfertigung und dem Einzel-Verkauf in den Apotheken getrennt. In diesem Fall ist das Medicinalgewicht dem gewöhnlichen Landesgewicht beinahe oder völlig gleich und das Pfund wird dann in 16 Unzen getheilt. Bei dem eigentlichen Apothekergewicht aber nimmt man nur einen Theil des Landesgewichts und theilt dieses Pfund in 12 Unzen oder 96 Drachmen oder 288 Scrupel oder 5760 Gran oder 7452 Aß." "Die deutschen Schriftsteller bedienen sich bei dem Mangel allgemeiner deutscher Maße meistens der Altfranzösischen, des Apothekergewichts, der metrischen Maße und Gewichte, die preußischen am allgemeinsten, die Baiern nicht selten der in ihren Staaten eingeführten." 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.The avoirdupois pound, on the other hand, is defined as 7000 grains. It is subdivided into 16 (avoirdupois) ounces, or 256 (avoirdupois) drachms. These ounces and drachms are not integer multiples of a grain. 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."Apothecaries Weights were the weights which Pharmaceutical Chemists (or Pharmacists) [in Australia] used exclusively until the late 1960s." "To those Pharmacists who were in practice before the 1960s, Apothecaries Weights were old friends." "Although fast becoming obsolete, the apothecary system for weighing and calculating pharmaceutical preparations is still used and must be taken into consideration." 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."An acre is not an acre, nor a bushel a bushel, if you travel but ten miles. A pound is not a pound, if you go from a goldsmith to a grocer; nor a gallon a gallon, if you go from the alehouse to the tavern. What purpose does this variety serve, or what necessity is there, which the difference of price would not better answer and supply?" 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."In most countries there are two kinds of Weights, one for the precious Metals, and the other for Merchandize, as the Troy and Avoirdupois Weights in England. 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 1850, an attempt was made in Ireland to solve this problem: "In relation to the weights and measures, a great innovation has been made, which, however, the College feels confident will receive the sanction of the public and the profession. [...] In the formularies, however, [of the Edinburgh Pharmacopœia], the Troy pound, with its well-known submultiples, has been retained, whereas it is now rejected by the Irish College, and its place supplied by the avoirdupois pound, the avoirdupois ounce being, like the Troy ounce, subdivided into eight drachms, and each of these, like the Troy drachm, into three scruples. [...] At present the two systems are in use with the apothecary, for his purchases are made in avoirdupois, and his sales generally, though not always, in Troy weight." See also p. xlvi, and a review of the work. In old merchants' handbooks, the former system is sometimes referred to as the pharmaceutical system and distinguished from the apothecaries' system."Im Königreich der Niederlande ist das Medicinal-Gewicht im Großen und das eigentliche Apotheker-Gewicht verschieden. Bei dem erstern gehören 8 Drachmen zu einer Once (Unze) und 128 zu einem Medicinal-Pond; die Drachme wird wie in Deutschland in 3 Scrupel oder 60 Grän getheilt. In dem eigentlichen Apotheker-Gewicht gehören auch 8 Drachemn zu einer Unze, aber nur 96 Drachmen zu einem Pond. Die Drachme selbst ist in beiden Gewichtsarten gleich [...]." E.g. in Copenhagen at some time the apothecaries' system was the Prussian one, while the pharmaceutical system was the Danish commercial system. "Das Apothekergewicht ist dem unter Berlin bemerkten gleich; im Großen aber werden Medicinalartikel nach Dän. Handelsgewicht verkauft."
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English-speaking countries
Weight + British Apothecaries' weights and conversions(Traditional troy-based version) Weight(symbol) Pound(, ″̶) Ounce(℥) Dram(drachm)(ʒ) Scruple(℈) Grain(gr) 1 12 ℥ 96 ʒ 288 ℈ 5,760 gr. 1 ℥ 8 ʒ 24 ℈ 480 gr. 1 ʒ 3 ℈ 60 gr. 1 ℈ 20 gr. In metric 373.3 g 31.1 g 3.89 g 1.296 g 64.8 mg + Proposed avoirdupois-based apothecaries' system, Dublin 1850 Pound( Ounce(℥) Drachm(ʒ) Scruple(℈) Grain(gr) 1 16 ℥ 128 ʒ 384 ℈ 7,000.00 gr. 1 ℥ 8 ʒ 24 ℈ 437.50 gr. 1 ʒ 3 ℈ 54.68 gr. 1 ℈ 18.22 gr. 453.6 g 28.3 g 3.5 g 1.2 g 64.8 mg + British Apothecaries' weights and conversions (avoirdupois version, 1864–1971) Weight(symbol) Pound(lb.) Ounce(oz.) Grain(gr.) 1 lb. 16 oz. 7,000 gr. 1 oz. 437.5 gr. In metric 453.6 g 28.3 g 64.8 mg
From pound down to the scruple, the units of the traditional English apothecaries' system were a subset of the units of the Roman weight system, although the troy pound and its subdivisions were slightly heavier than the Roman pound and its subdivisions. Similar systems were used all over Europe, but with considerable local variation described below under Variants. The traditional English apothecaries' system of weights is shown in the first table in this section: the pound, ounce and grain were identical to the troy pound, ounce and grain (also used to measure weights of precious metals; distinct from the avoirdupois pounds and ounces that were used for measurements of other goods.) The confusing variety of definitions and conversions for pounds and ounces is covered elsewhere in a table of pound definitions.
The Irish pharmacopœia of 1850 rejected the use of the troy pound and instead adopted the use in its formulae of the avoirdupois pound, divided into 16 avoirdupois ounces, with the avoirdupois ounce subdivided into eight drachms, each of three scruples. This innovation was intended to unify the units used by apothecaries for sale with the avoirdupois units that they used for purchase, and that were used by other professions such as manufacturing chemists. To allow effective use of the new system, new weight pieces were produced. Since an avoirdupois ounce corresponds to 28.35 g, the proposed system was very similar to that in use in Portugal and Spain, and in some locations in Italy. But it would have doubled the value of the avoirdupois drachm (an existing unit, but by then only used for weighing silk). Therefore, it conflicted with other non-standard variations that were based on that nearly obsolete unit.
The Irish proposal was not widely adopted, but British legislation, in the form of the Medical Act 1858 (21 & 22 Vict. c. 90), was more radical: it prescribed the use of the avoirdupois system for the United Kingdom (then including Ireland), with none of the traditional subdivisions. This innovation was first used in the United British pharmacopœia of 1864, which recommended the adoption in pharmacy of the imperial avoirdupois pound of 7000 grains and ounce of 437.5 grains, and discontinuation of the drachm and scruple. In practice, however, the old apothecaries' system based on divisions of the troy pound, or of the troy ounce of 480 grains, was still widely used until it was abolished by the Weights and Measures Act 1976 (c. 77), since when it may only be used to measure precious metals and stones. (The troy pound had already been declared illegal for most other uses by the Weights and Measures Act 1878 (41 & 42 Vict. c. 49), but this act allowed the sale of drugs by apothecaries' weight as an exception.)
Apothecaries' units of any kind became obsolete in the UK with the mandatory use of metric drug measurements from January 1, 1971.
In the United States, the apothecaries' system remained official until it was abolished in 1971 in favour of the metric system.
Volume + Measures: U.S. (& U.K. 1809–1864) Pint Fluid ounce Fluid dram Fluid scruple Minim 1 pt. 16 ƒ℥ 128 ƒʒ 384 ƒ℈ 7,680 1 ƒ℥ 8 ƒʒ 24 ƒ℈ 480 1 ƒʒ 3 ƒ℈ 60 1 ƒ℈ 20 473 mL 29.6 mL 3.70 mL 1.23 mL 0.0616 mLKey: pt. = pint + Measures: U.K. (Imperial; 1864–1971) Imperial gallon Imperial pint Fluid ounce Fluid drachm Minim 1 C 8 O 160 fl. oz. 1280 fl. dr. 38,400 min. 1 O 20 fl. oz. 160 fl. dr. 9,600 min. 1 fl. oz. 8 fl. dr. 480 min. 1 fl. dr. 60 min. 20 min. 4546 mL 568 mL 28.4 mL 3.55 mL 0.059 mL Key: C = (gallon); O = octarius or octavius (pint)
English-speaking countries also used a system of units of fluid measure, or in modern terminology volume units, based on the apothecaries' system. Originally, the terms and symbols used to describe the volume measurements of liquids were the same as or similar to those used to describe weight measurements of solids (for example, the pound by weight and the fluid pint were both referred to with Latin libra, symbol ). A volume of liquid that was approximately that of an apothecaries' ounce of water was called a fluid ounce, and was divided into fluid drachms and sometimes also fluid scruples. The smallest unit of liquid volume was traditionally a drop (Latin gutta). Although nominally defined as a sixtieth of the fluid drachm, in practice the drop was a not a standardized unit of volume but was measured by means of releasing literal drops of liquid from the lip of a bottle or vial.