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Webster 1913 Edition
Caesium
caesium
,Cæ′si-um
(sē′zē̍-ŭm)
, Noun.
[NL., from L.
caesius
bluish gray.] (Chem.)
A rare alkaline metal found in mineral water; – so called from the two characteristic blue lines in its spectrum. It was the first element discovered by spectrum analysis, and is the most strongly basic and electro-positive substance known. Symbol Cs. Atomic number 55. Atomic weight 132.6.
Syn. – cesium, Cs