congruent transition

https://doi.org/10.1351/goldbook.C01264
A transition in which the two-phase equilibrium of @M03821@, vaporization or allotropism of a compound involves phases of the same composition.
Source:
PAC, 1994, 66, 577. (Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)) on page 579 [Terms] [Paper]