Period 6 element form, as an X-ray radiocontrast agent for imaging the human gastrointestinal tract. Soluble barium compounds are poisonous due to release of the soluble barium ion, and have been used as rodenticides. New uses for barium continue to be sought. It is a component of some "high temperature" YBCOsuperconductors, and electroceramics. The lanthanide or lanthanoid (IUPAC nomenclature) series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium. These fifteen elements, along with the chemically similar elements scandium and yttrium, are often collectively known as the rare earth elements. The informal chemical symbol Ln is
Metallic dragon and adamantine dragons for brass and bronze, and released the latter dragons in a later book alongside cobalt, mercury, mithral, orium, and steel dragons. The classification of "metallic dragons" was used in the "Advanced Dungeons & Dragons" second edition "Monstrous Manual" (1993), although the gold(en) dragon first appeared in the original "Dungeons & Dragons" "white box" set (1974) and the other dragons comprising the category had been in print since the first edition "Monster Manual" (1977). The term was continued in use in the third edition and fourth edition "Monster Manual". Although weaker than many other varieties of dragonkind, brass