Strontium titanate is an oxide of strontium and titanium with the chemical formula SrTiO. Strontium chloride (SrCl) is a salt of strontium and chloride. Insoluble radium compounds coprecipitate with all barium, most strontium, and most lead compounds. They contain large amounts of rubidium, strontium and barium. Tritium causes less concern than other radioactive substances such as strontium, caesium and iodine. These elements include vanadium, manganese, iron, cobalt, copper, zinc, selenium, strontium and molybdenum. Barium is chemically similar to magnesium, calcium, and strontium, but even more reactive. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. The strontium and barium will be fixed in the perovskite. Bromous acids and bromites are very unstable, although the strontium and barium bromites are known. The content of bismuth and strontium creates some chemical issues. Many of the fission products (such as caesium, zirconium and strontium) remain in the salt. The metal is produced commercially by reducing strontium oxide with aluminium. It also forms from the decomposition of strontium carbonate SrCO. Celestine or celestite is a mineral consisting of strontium sulfate (SrSO).