This is our highest purity grade of Caesium Iodide (CAS # 7789-17-5), with a molecular weight of 261.789 g/mol. It is commonly used in analytical chemistry, infrared spectroscopy and X-ray diffraction applications. It is also used in scintillation counters, fluorometers and luminescence detectors. Our Caesium Iodide 99.9% is of the highest quality available.