Barium hydroxide, it absorbs very little CO in aqueous solutions and is therefore insensitive to atmospheric fluctuations. This property is used in calibrating pH equipment. Volatile barium compounds burn with a green to pale green flame, which is an efficient test to detect a barium compound. The color results from spectral lines at 455.4, 493.4, 553.6, and 611.1 nm. Organobarium compounds are a growing field of knowledge: recently discovered are dialkylbariums and alkylhalobariums. Barium found in the Earth's crust is a mixture of seven primordial nuclides, barium-130, 132, and 134 through 138. Barium-130 undergoes very slow radioactive decay to xenon-130 by
Barium sulfate mixture and make it hard to see the color of the indicator. Barium sulfate added to the mixture binds with these particles, making them heavier so they fall to the bottom, leaving a clearer solution. In colorimetry, barium sulfate is used as a near-perfect diffuser when measuring light sources. In metal casting, the moulds used are often coated with barium sulfate in order to prevent the molten metal from bonding with the mould. It is also used in brake linings, anacoustic foams, powder coatings, and root canal filling. Barium sulfate is used as a catalyst support when selectively hydrogenating functional