## Wikipedia - Soluzione ideale ideal mixture

https://doi.org/10.1351/goldbook.I02938
A mixture of substances B, C, ... is called an ideal mixture when $$a_{\text{B}}=x_{\text{B}}$$, $$a_{\text{C}}=x_{\text{C}}$$, ... or $$f_{\text{B}}=1$$, $$f_{\text{C}}=1$$ where $$a_{\text{B}}$$ and $$f_{\text{B}}$$ are the @R05256@ and the @A00116@, respectively, of a substance B in a liquid or solid mixture.
Source:
PAC, 1994, 66, 533. (Standard quantities in chemical thermodynamics. Fugacities, activities and equilibrium constants for pure and mixed phases (IUPAC Recommendations 1994)) on page 543 [Terms] [Paper]