Page "Mole (unit)" Paragraph 12

Charles Frédéric Gerhardt ( 1816 – 56 ), Henri Victor Regnault ( 1810 – 78 ) and Stanislao Cannizzaro ( 1826 – 1910 ) expanded on Berzelius ' works, resolving many of the problems of unknown stoichiometry of compounds, and the use of atomic weights attracted a large consensus by the time of the Karlsruhe Congress ( 1860 ).

The convention had reverted to defining the atomic weight of hydrogen as 1, although at the level of precision of measurements at that time — relative uncertainties of around 1 % — this was numerically equivalent to the later standard of oxygen = 16.

However the chemical convenience of having oxygen as the primary atomic weight standard became ever more evident with advances in analytical chemistry and the need for ever more accurate atomic weight determinations.