But that's really the last term with the prefix, I promise! DESALINATION is the removal of all salts dissolved in water. And what do you need for that? Take a cation exchanger which exchanges the cations of the salts present in the water for hydrogen ions and an anion exchanger which changes the anions present in the water for hydroxide ions. We will soon be looking at hydroxide ions in more detail; for now, it's enough to know that this is a negatively charged ion that is produced when water and bases react. Speaking of bases, the work of the above-mentioned cation exchanger is known as debasing, and that of the anion exchanger as deacidification. Debasing and deacidification together finally form DESALINATION, resulting in fully deionized water. But be careful, don't confuse DESALINATION with softening: When softening, the salts are only replaced and when DESALINATED, they are actually removed.