For example, the formula H 2 O shows that a water molecule contains two hydrogen atoms and one oxygen atom.

THE general formula devised by Messrs. Ganguillet and Kutter for caculating the flow of water in both large and small channels, under varied conditions, was brought under the notice of English ...

Here is the formula for hydrated copper(II) sulfate. Notice that water of crystallisation is separated from the main formula by a dot.