The chemical potential of a substance B in a mixture of substances B, C ... is related to the Gibbs energy G of the mixture by: \[\mu _{\text{B}}=(\frac{\partial G}{\partial n_{\text{B}}})_{T,p,n_{\text{C}\neq \text{B}}}\] where T is the thermodynamic temperature, p is the pressure and nB, nC, ... are the amounts of substance of B, C, ... . For a pure substance B, the chemical potential µB* is given by: \[\mu _{\text{B}}^{*}=\frac{G^{*}}{n_{\text{B}}}=G_{\text{m}}^{*}\] where Gm* is the molar Gibbs energy, and where the superscript * attached to a symbol denotes the property of the pure substance. The superscript Θ or ° attached to a symbol may be used to denote a standard thermodynamic quantity.