Iron(II) hydroxide
Iron(II) hydroxide or ferrous hydroxide is an inorganic compound with the formula Fe(OH). It is produced when iron(II) salts, from a compound such as iron(II) sulfate, are treated with hydroxide ions. Iron(II) hydroxide is a white solid, but even traces of oxygen impart a greenish tinge. The air-oxidized solid is sometimes known as "green rust".
Hydron (chemistry)
The hydrated form of the hydrogen cation, the hydronium (hydroxonium) ion , is a key object of Arrhenius' definition of acid. Other hydrated forms, the Zundel cation which is formed from a proton and two water molecules, and . The hydron itself is crucial in more general Brønsted–Lowry acid–base theory, which extends the concept of acid–base chemistry beyond aqueous solutions.