Iron(II) sulfite is an ionic compound that results from the combination of an iron (FE) (II) ion with a sulfite ion (SO3). The Fe(II) ion has a +2 charge, and the sulfite ion has a -2 charge. Since these charges balance, only one sulfite ion and one Fe(II) ion are combined to make iron(II) sulfite.
Iron has more than one oxidation state. As a result, when discussing compounds that contain iron ions, it is important to specify the oxidation state. Iron has two oxidation states, Fe(II) and Fe(III). Sulfites are ions consisting of three oxygen atoms and a single sulfur atom. Sulfites are distinct from sulfur trioxides even though both contain the same number of atoms, because sulfites are ions with a charge of -2.
Iron(II) sulfite is used in chemistry and biochemistry applications. A common use of iron(II) sulfite is in iron sulfite agar, which is a medium that can be used to grow bacteria. By using iron sulfite agar, scientists can detect the growth of a specific type of microbe that causes food to spoil. The agar is low in oxygen content, so only anaerobic microbes are able to grow in it. The agar is typically combined with particular dyes that make it easier to detect the growing microbes.