isosteric enthalpy of adsorption

https://doi.org/10.1351/goldbook.I03313
When the addition of the differential amount of component i dniσ or dnis is effected at constant pressure p, the differential molar
enthalpy
of adsorption, ΔaHiσ or ΔaHis also called the isosteric
enthalpy
of adsorption (qst) is defined as: ΔaHiσ=qst,σ=UiσHig ΔaHis=qst,σ=HiσHig where His=(Hsnis)T,p,m,njs and Hig is the partial molar
enthalpy
of component i in the gas phase, i.e. (Hgnig)T,p,nig
Source:
PAC, 1972, 31, 577. (Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry) on page 603 [Terms] [Paper]