Barium is a soft, silvery-white metal, with a slight golden shade when ultra pure. The silvery-white color of barium metal rapidly vanishes upon oxidation in air yielding a dark gray oxide layer.
Barium compounds that are water or acid soluble are highly poisonous. Barium powder can ignite spontaneously in air.
Barium sulfate, used in x-ray imaging,
is highly insoluble in water, and is therefore nontoxic and completely removed from the digestive tract.