Note 92 — Chapter VI · THE AGE OF MODERN CHEMISTRY
Reading edition
Since hydrogen is the lightest of all known substances, the unit, Hydrogen = 1, was at one time usually employed. However, it was seen to be more convenient to express the atomic weights in terms of the weight of the oxygen-atom, and the unit, Oxygen = 16 is now always employed. This value for the oxygen-atom was chosen so that the approximate atomic weights would in most cases remain unaltered by the change.