We'd like to use analytics cookies to understand which symbols people look up, so we know what to research next. They are not used for advertising and we set none of them unless you say yes. What we store.
A small circle, often struck through, raised after a quantity.
Also known as: Standard state notation, Plimsoll symbol, Standard conditions symbol, Circle after a delta H
The raised circle says a thermodynamic quantity is quoted at the standard state — one bar and unit activity, and *not* a specified temperature. Assuming standard state means 25 °C is the commonest misreading; the temperature must be stated separately.
Denotes that a thermodynamic quantity refers to the standard state: a pressure of one bar and unit activity for solutes.
Contexts: Laboratory
Does not specify a temperature; standard-state values are tabulated at 298.15 K by convention but the symbol itself carries no temperature.
Contexts: Laboratory
Is written as a plain circle, a struck-through circle or a superscript circle depending on the typography available; IUPAC's preferred form is the struck circle.
Contexts: Laboratory
A small circle raised to the upper right of a quantity symbol, often with a short horizontal stroke through its centre.