The solubility of barium sulfate BaSO4 in water at room temperature 25C is very low. It is approximately 2.4 mg/L or 2.4 ppm parts per million . This means that only about 2.4 milligrams of BaSO4 will dissolve in 1 liter of water at room temperature. Barium sulfate is considered to be an insoluble salt due to its extremely low solubility.