thallium

[ thal-ee-uhm ]

noun

, Chemistry.

1. a soft, malleable, rare, bluish-white metallic element: used in the manufacture of alloys and, in the form of its salts, in rodenticides. : Tl; : 204.37; : 81; : 11.85 at 20°C.

thallium

/ ˈθælɪəm /

noun

1. a soft malleable highly toxic white metallic element used as a rodent and insect poison and in low-melting glass. Its compounds are used as infrared detectors and in photoelectric cells. Symbol: Tl; atomic no: 81; atomic wt: 204.3833; valency: 1 or 3; relative density: 11.85; melting pt: 304°C; boiling pt: 1473±10°C

thallium

/ thăl′ē-əm /

1. A soft, malleable, very poisonous metallic element that is used in photography, in making low-melting and highly refractive glass, and in treating skin infections. Atomic number 81; atomic weight 204.38; melting point 303.5°C; boiling point 1,457°C; specific gravity 11.85; valence 1, 3.
2. See Periodic Table

Word History and Origins

Origin of thallium¹

1860–65; < New Latin, equivalent to thall- (< Greek thallós green stalk) + -ium -ium; named after green line in its spectrum

Word History and Origins

Origin of thallium¹

C19: from New Latin, from Greek thallos a green shoot; referring to the green line in its spectrum

Example Sentences

Thallium is a rare metal, found in small quantities in some varieties of iron and copper pyrites, and in some lithia micas.

From Project Gutenberg

A stream of incandescent thallium-vapour passes between them, the magnified image of which is now seen upon the screen.

From Project Gutenberg

Light of one degree of refrangibility—that corresponding to this particular green—is emitted by the thallium-vapour.

From Project Gutenberg

If we add to the silver in our camera a bit of thallium, we shall obtain the light of both metals.

From Project Gutenberg

After waiting a little, we see that the green of the thallium lies midway between the two greens of the silver.

From Project Gutenberg