Thallium
Pronunciation : Thal"li*um
Part of Speech : n.
Etymology : [NL., fr. Gr. green line in its spectrum.] (Chem.)
Definition : Defn: 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.
Source : Webster's Unabridged Dictionary, 1913