Barium nitrate fighters, such as the Hawker Hurricane and Supermarine Spitfire, during the Battle of Britain. It is also used in the manufacturing process of barium oxide, the vacuum tube industry and for green fire in pyrotechnics. Like all soluble barium compounds, barium nitrate is toxic by ingestion or inhalation. Solutions of sulfate salts such as Epsom salts or sodium sulfate may be given as first aid for barium poisoning, as they precipitate the barium as the insoluble (and non-toxic) barium sulfate. Inhalation may also cause irritation to the respiratory tract. While skin or eye contact is less harmful than ingestion or
Barium borate 1 GW/cm at 1064 nm and 500 MW/cm at 355 nm. Beta barium borate, β-BaBO, is a nonlinear optical material transparent in the range ~190–3300 nm. It can be used for spontaneous parametric down-conversion. Its Mohs hardness is also 4.5. Barium borate has strong negative uniaxial birefringence and can be phase-matched for type I ("ooe") second-harmonic generation from 409.6 to 3500 nm. The temperature sensitivity of the indices of refraction is low, leading to an unusually large (55 °C) temperature phase-matching bandwidth. Barium borate can be prepared by reaction of an aqueous solution of boric acid with barium hydroxide. The