Barium. Be; one of the alkaline earth metals. At. wt. 137.36; at. no. 56; valence 2. Discovered by Davy in 1808.

Yellowish-white, slightly lustrous lumps; somewhat malleable; very easily oxidizable; must be kept under petroleum or other oxygen free liquid to exclude air. d. 3.5. m. 850°. b. 1140°. Decomposed by water or alcohol with evolution of hydrogen.

Solns. of soluble barium salts give a white ppt. with H₂SO₄ or soluble sulfates; they also color nonluminous flame green.

Caution: All water or acid soluble barium compounds are poisonous!