Barium green color. Barium sulfate is used as an insoluble additive to oil well drilling fluid, as well as in a purer form, as X-ray radiocontrast agents for imaging the human gastrointestinal tract. The soluble barium ion and soluble compounds are poisonous, and have been used as rodenticides. Barium is a soft, silvery-white metal, with a slight golden shade when ultrapure. The silvery-white color of barium metal rapidly vanishes upon oxidation in air yielding a dark gray oxide layer. Barium has a medium specific weight and good electrical conductivity. Ultrapure barium is very difficult to prepare, and therefore many properties of
Barium ferrite used in applications such as recording media, permanent magnets, and magnetic stripe cards (credit cards, hotel keys, ID cards). Due to the stability of the material, it is able to be greatly reduced in size, making the packing density much greater. Earlier media devices utilized doped acicular oxide materials to yield the coercivity values necessary to record. In recent decades, barium ferrite has replaced acicular oxides; without any dopants, the acicular oxides produce very low coercivity values, making the material very magnetically soft, while barium ferrite's higher coercivity levels make the material magnetically hard and thus a superior choice for