https://doi.org/10.1351/goldbook.S05449
The ionic form of an
ion exchanger
in which the counter-ions
are neither hydrogen nor hydroxide ions. When only one valence
is possible for the counter-ion, or its exact form or charge is not known, the symbol or the name of the counter-ion without charge is used, e.g. sodium-form or Na-form, tetramethylammonium-form, orthophosphate-form. When one of two or more possible forms is exclusively present, the oxidation state
may be indicated by a Roman numeral, e.g. FeII form, FeIII form.