Where Did We Dig Up the Mole

Equivalent masses (and the related concept of normality ) have gradually disappeared from modern chemistry texts in favor of a definition based directly on numbers of particles (atoms, molecules, ions, electrons), and this is truly ironic. 

The term mole was first introduced by Wilhelm Ostwald in 1901. It is derived from the Latin for mass, hump, or pile (the term molecule, introduced by Pierre Gassendh in the early seventeenth century has the same root presumably it means a mass of atoms). Specifically, Ostwald used the term to represent the formula weight of a substance in grams 36.5 g of HCl is one mole. The formal definition of the mole adopted by the Fourteenth Conference Generale des Poids et Mesures in 1971 is the amount of a substance of a system that contains as many elementary entities as there are atoms in 0.012 kilograms of carbon-12. The rich irony is that Ostwald fiercely resisted the atomic concept at the time Boltzmann committed suicide in 1906 but his mole is now defined explicitly in terms of atoms. 

---