The experiments made on the mutual electrical relations of bodies have taught us that they can be divided into two classes: electropositive and electronegative. The simple bodies which belong to the first class, as well as their oxides, always take up positive electricity when they meet simple bodies or oxides belonging to the second class; and the oxides of the first class always behave with the oxides of the other like salifiable bases with acids.
Jons Jacob Berzelius
