https://doi.org/10.1351/goldbook.E02177
Quantity characterizing the equilibrium of a chemical reaction and defined by an expression of the type \(K_{x}=\underset{\begin{array}{c} \text{B} \end{array}}{\Pi }x_{\text{B}}^{\nu _{\text{B}}}\), where \(\nu _{\text{B}}\) is the @S06025@ of a reactant (negative) or product (positive) for the reaction and \(x\) stands for a quantity which can be the equilibrium value either of pressure, fugacity, @A00295@, amount fraction, molality, @R05256@ or reciprocal @A00019@ defining the pressure based, fugacity based, concentration based, amount fraction based, molality based, @R05256@ based or @S05915@ (then denoted \(K^{\unicode{x26ac}}\)), respectively.
Source:
Green Book, 2nd ed., p. 50 [Terms] [Book]