Barium sulfate
Barium sulfate as a contrast medium was evolved from the prior use of bismuth preparations which were too toxic. The use of bismuth preparations had been described as early as 1898. Barium sulfate as a contrast medium in medical practice was introduced largely as a result of the works of Krause a director of the Bonn Polyclinic, now the medical faculty of the University of Bonn and his colleagues Bachem and Gunther. In a paper read in 1910 at the radiological congress they advocated for the use of barium sulfate as an opaque contrast medium in medicine.