Equilibria involving the addition of a gaseous ligand

A special notation is used for constants describing equilibria that involve the addition of a gaseous ligand, as outlined in Eq.(11.20). 

The subscript p can be combined with any other notations given above. Example  

In cases where the subscripts become complicated, it is recommended that K or P be used with or without subscripts, but always followed by the equation number of the equilibrium to which it refers. 

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