Apothecaries' system measure precious metals and stones. (The troy pound was already declared illegal for most other uses by the Weights and Measures Act of 1878.) In the US, the metric system replaced the apothecaries' system in the United States Pharmacopoeia of 1971. Apothecaries' system 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 recipes, 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
Heavy metals metals in form or appearance"). This suggestion was ignored; the new elements came to be recognised as metals, and the term metalloid was then used to refer to nonmetallic elements and, later, elements that were hard to describe as either metals or nonmetals. An early use of the term "heavy metal" dates from 1817, when the German chemist Leopold Gmelin divided the elements into nonmetals, light metals, and heavy metals. Light metals had densities of 0.860–5.0 g/cm; heavy metals 5.308–22.000. The term later became associated with elements of high atomic weight or high atomic number. It is sometimes used interchangeably