Fluorine is used by a number of plants to manufacture toxins ( see that element ) but in humans only functions as a local ( topical ) hardening agent in tooth enamel, and not in an essential biological role.
12.
The radiocarbon dates from his excavations led to a shift of almost five centuries in Early Bronze Age chronology in this area, while the study of the Early Bronze Age blades from Buccino ( Salerno ) was one of the first to document the use of arsenic as a hardening agent in early bronze metallurgy.
