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Material World
Element · Tl

Thallium

A metal whose main historical use was killing things, and which is now mostly encountered as a problem.

Thallium is a soft, grey metal that is severely toxic — colourless, tasteless in solution, and readily absorbed through the skin. Its poisoning symptoms are diffuse enough to have been mistaken for other illnesses, which gave it a long and unfortunate history as a murder weapon and earned it the nickname of the poisoner's poison.

It is recovered as a by-product of zinc and lead smelting, and much of the effort surrounding it is about capturing it before it disperses rather than about using it.

Uses

Thallium sulfate was an effective rodenticide and insecticide, and that was for a long time its principal use. It has been banned for that purpose in most countries because it is as poisonous to people as it is to rats.

Its surviving legitimate uses are specialised. Thallium-doped sodium iodide crystals are standard scintillation detectors for gamma radiation. Thallium bromo-iodide transmits infrared and is used in optics. Thallium-201 is a cardiac imaging tracer, and thallium is a component of some high-temperature superconductors.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is sourced from

  • Zinc — element · captured from the flue dusts of zinc smelting before it disperses
  • Lead — element · and from lead smelting, by the same route

is used as

  • Medical imaging — application · thallium-201 as a cardiac imaging tracer

is produced by

  • Smelting — process · captured from the flue dusts, before it disperses

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • PubChem
    US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors
  • NIST — National Institute of Standards and Technology
    United States Department of Commerce · US Government work — public information, credit requested

Questions this page answers

Where it comes from, and what it becomes

Follow Thallium back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Thallium → is produced by (captured from the flue dusts, before it disperses) → Smelting → takes as input (as the element removed, not added) → Oxygen → is produced by (the largest output by tonnage, and the reason air separation units sit beside steelworks) → Air separation → takes as input (the feedstock, and an unusual one in being free, unlimited and available anywhere — the cost is entirely the energy to liquefy it) → Air
  • Thallium → is sourced from (captured from the flue dusts of zinc smelting before it disperses) → Zinc → is produced by (as the oxide, which is then reduced — roasting is the step that makes zinc sulfide smeltable) → Roasting → takes as input (a copper sulfide; roasting drives off the sulfur that would otherwise prevent reduction) → Chalcopyrite
  • Thallium → is sourced from (and from lead smelting, by the same route) → Lead → is produced by (as the oxide, from galena, by the same route) → Roasting → takes as input (a copper sulfide; roasting drives off the sulfur that would otherwise prevent reduction) → Chalcopyrite
  • Thallium → is produced by (captured from the flue dusts, before it disperses) → Smelting → takes as input (roasted to drive off sulfur, then reduced to copper) → Chalcopyrite
  • Thallium → is produced by (captured from the flue dusts, before it disperses) → Smelting → takes as input (reduced with carbon to metallic tin) → Cassiterite
  • Thallium → is produced by (captured from the flue dusts, before it disperses) → Smelting → takes as input (reduced with coke in a blast furnace) → Hematite

These are the most distinct paths back. Thallium can be traced through others besides.

Downstream — what it becomes