Table 1.

Classification of ionic DESs ^a.

Class	Composition b
Type I	Cat+X−zMClx
Type II	Cat+X−zMClx·yH2O
Type III	Cat+X−zRZ
Type IV	${\mathrm{MCl}}_{\mathrm{x}}+\mathrm{RZ}\to {\mathrm{MCl}}_{\mathrm{x}-1}^{+}·\mathrm{RZ}+{\mathrm{MCl}}_{\mathrm{x}+1}^{-}$

^a according to the classification proposed by Abbott and colleagues [1]. ^b Cat⁺ is an ammonium, a phosphonium, or a sulfonium cation (most often a quaternary ammonium, a pyridinium or an imidazolium); X⁻ is a halide anion (most often Cl⁻); MCl_x is a metal chloride salt; RZ is an organic amide (e.g., urea), a carboxylic acid (e.g., oxalic acid) or an alcohol (e.g., ethylene glycol).