Chem. [f. L. cæsium, neuter of cæsius bluish grey.] One of the elementary bodies; a rare alkali-metal discovered by spectrum-analysis in 1860–1 by Bunsen and Kirchhoff; so called from two distinctive lines in the spectrum given by its compounds. Symbol Cs. Used attrib., as in cæsium compounds.
1861. Lond. & Edinb. Philos. Mag., Ser. IV. No. 21. 86. A faint blue line not due to strontium or potassium or to the lately discovered cæsium.
1862. Timbs, Year-bk. of Facts, 188. Cæsium and Rubidium. The new alkaline metals … described … in the Philosophical Magazine.
1864. Lyell, Inaug. Addr., in Reader, 17 Sept., 358/1. It was necessary to evaporate fifty tons of water to obtain 200 grains of what proved to be two new metals…. He [Professor Bunsen] named the first cæsium, from the bluish-grey lines which it presented in the spectrum.
1873. Fownes, Chem., 350. Caesium carbonate is soluble in absolute alcohol.
