But Water is not the only medium/solvent where Dissociation can be observed or measured, but one of the most important!
There are quite a lot, and there are even “Non-Solutions” where Ions from Dissociation exist as in “Fused Salts
And even in the “Gas-Phase” you can produce Ions and define it also as Dissociation; for an Example you may think of the Vacuum of a “Mass-Spectrometer
” (maybe a little exotic of this kind). Also in the “Galactic Space” a numerous Ions of different kind exist.
Beside your textbook you may also visit: "Dissociation