Formula unit Formula unit A formula unit in chemistry is the empirical formula of any ionic or covalent network solid compound used as an independent entity for stoichiometric calculations. It is the lowest whole number ratio of ions represented in an ionic compound. Examples include ionic NaCl and KO and covalent networks such as SiO and C (as diamond or graphite). Ionic compounds do not exist as individual molecules; a formula unit thus indicates the lowest reduced ratio of ions in the compound. A "chemical formula" shows the kinds and numbers of atoms in the smallest representative unit of a substance. In
Compound analgesic Compound analgesic Compound analgesics are those with multiple active ingredients; they include many of the stronger prescription analgesics. Active ingredients that have been commonly used in compound analgesics include: Several such formulations have disappeared from over-the-counter status in drug store aisles and other retail outlets. One example is APC (aspirin, phenacetin, and caffeine) compound tablets common from the 1940s to 1983; because of harmful side effects of phenacetin, Anacin in the U.S. was reformulated to eliminate it; while Vincent's APC is no longer sold. Some others have been judged to contribute too often to substance abuse. Another example is Bex,