thal·​li·​um | \ ˈtha-lē-əm How to pronounce thallium (audio) \

Definition of thallium

: a soft poisonous metallic element that resembles lead in physical properties, occurs sparsely in a number of common ores, and is used chiefly in the form of compounds especially in photosensitive devices and formerly as a pesticide — see Chemical Elements Table

Examples of thallium in a Sentence

Recent Examples on the Web

The substance that condensed inside the tube, upon analysis, contained an abnormally large amount of thallium. Sophia Chen, WIRED, "New Analysis Techniques Unearth a Trove of Unusual Minerals," 1 July 2019 But a second hair from March 1995 showed Zhu Ling had ingested large doses of thallium constantly for about two weeks. Jennifer Ouellette, Ars Technica, "Study brings us one step closer to solving 1994 thallium poisoning case," 25 Dec. 2018 Ash found that Zhu Ling had received many doses of toxic thallium, increasing in frequency and concentration over time. Jennifer Ouellette, Ars Technica, "Study brings us one step closer to solving 1994 thallium poisoning case," 25 Dec. 2018 Lead, arsenic, boron, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, selenium, thallium, and uranium are among the chemicals and heavy metals listed with coal ash deposits. Grace Schneider, The Courier-Journal, "An Indiana county is paying a steep price for burying toxic coal ash," 18 May 2018 Ash storage sites at the plant are leaking into surface water and groundwater upstream of drinking water intakes for more than 1 million people in the Charlotte region, the report says, calling the thallium and radium results alarming. Deon Roberts, charlotteobserver, "Groundwater at Duke Energy coal ash sites faulted for high radioactivity levels | Charlotte Observer," 20 Mar. 2018 There, in Islamabad, Naeem had a thallium stress test to assess the damage. Sorayya Khan, Longreads, "The Cities in Me," 8 Feb. 2018 One of Koremlu’s active ingredients was thallium acetate. Kat Eschner, Smithsonian, "Three Horrifying Pre-FDA Cosmetics," 26 June 2017 Yes, Dr. Li had specialized knowledge and access to thallium but as a Joann Curley proves, such training isn’t really necessary for a determined killer. Deborah Blum, WIRED, "The Chemist as Murderer," 23 Feb. 2011

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'thallium.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of thallium

1861, in the meaning defined above

History and Etymology for thallium

New Latin, from Greek thallos green shoot; from the bright green line in its spectrum

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Statistics for thallium

Last Updated

8 Jul 2019

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Time Traveler for thallium

The first known use of thallium was in 1861

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More Definitions for thallium


thal·​li·​um | \ ˈthal-ē-əm How to pronounce thallium (audio) \

Medical Definition of thallium

: a sparsely but widely distributed poisonous metallic element that resembles lead in physical properties and is used chiefly in the form of compounds in photoelectric cells or as a pesticide symbol Tl — see Chemical Elements Table

More from Merriam-Webster on thallium

Rhyming Dictionary: Words that rhyme with thallium Encyclopedia article about thallium

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