CESIUM Cs CESIUM is used for; Bunsen and Kirchhoff named the element cesium, from the Latin word 'caesius' meaning sky blue, after the blue lines they saw in the spectrum. The Latin spelling isstill reflected in British English where cesium is spelt 'caesium.' In 1861 Bunsen and Kirchhoff also discovered rubidium by the same method. CESIUM is used for; Combines with oxygen and removes traces of gases from vacuum tubes Robert Busen and Gustav Kirchhoff Discovered in 1860 CESIUM Cs 55 atomic number CESIUM 132.9054 mass number Caesium is found in the minerals pollucite and lepidolite. Pollucite is found in great quantities at Bernic Lake,Manitoba, Canada and in the USA, and from this source the element can be prepared. However, most commercialproduction is as a by-product of lithium product Cs represents cesium its atomic number is 55 and mass number is 132.9054. It was found in the minerals pollucite and lepidolite is found in great quantities at Bemic Lake, Manitoba, Canada and in the USA