thallium

[ thal-ee-uhm ]

nounChemistry.

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

Origin of thallium

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

Words Nearby thallium

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use thallium in a sentence

thallium is a rare metal, found in small quantities in some varieties of iron and copper pyrites, and in some lithia micas.
A Textbook of Assaying: For the Use of Those Connected with Mines. | Cornelius Beringer and John Jacob Beringer
A stream of incandescent thallium-vapour passes between them, the magnified image of which is now seen upon the screen.
Six Lectures on Light | John Tyndall
Light of one degree of refrangibility—that corresponding to this particular green—is emitted by the thallium-vapour.
Six Lectures on Light | John Tyndall
If we add to the silver in our camera a bit of thallium, we shall obtain the light of both metals.
Six Lectures on Light | John Tyndall
After waiting a little, we see that the green of the thallium lies midway between the two greens of the silver.
Six Lectures on Light | John Tyndall

British Dictionary definitions for thallium

thallium

/ (ˈθælɪəm) /

noun

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

Origin of thallium

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

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for thallium

thallium

[ thăl′ē-əm ]

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. See Periodic Table.

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