Ion Exchange Fact Sheet


Water is the universal solvent that is able to dissolve a little bit of everything it touches. It could, therefore, be said that “pure” water does not exist. Even the most highly processed and purified water still contains trace levels of gases, salts or minerals that have been leached from its containment vessel or absorbed from the surrounding air. Salts are formed naturally when acidic rain water is neutralized by alkaline soil strata. Common salt (also called table salt) is sodium chloride (NaCl), but salt also refers to compounds containing potassium (K), calcium (Ca), iron (Fe), carbonates (CO32-), nitrates (NO31-) and many other combinations of elements.

When salts dissolve in water, they separate into charged particles called ions. A positively charged particle is a cation and a negative ion is an anion. Calcium (Ca2+), magnesium (Mg2+) and sodium (Na1+) are examples of cations. Chloride (Cl1-), nitrate (NO31-) and sulfate (SO42-) are examples of anions. The number of charges on an ion indicates the number of ‘counter-ions’ it will share in any reaction. Calcium ion, for instance requires two ‘counter-ions’ of chloride (CaCl2) but only one sulfate (CaSO4) because the final salt molecule must maintain a net neutral charge . Sulfate, for example, would require two sodium ions (Na2SO4) to balance the ionic charge for sodium sulfate.