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Webster 1913 Edition
Thallium
Thal′li-um
,Noun.
[NL., fr. Gr. [GREEK] young or green shoot or branch, twig. So called from a characteristic bright
green
line in its spectrum.] (Chem.)
A rare metallic element of the aluminium group found in some minerals, as certain pyrites, and also in the lead-chamber deposit in the manufacture of sulphuric acid. It is isolated as a heavy, soft, bluish white metal, easily oxidized in moist air, but preserved by keeping under water. Symbol Tl. Atomic weight 203.7.