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Material World
Element · Ar

Argon

The cheapest inert atmosphere available, because it is already a percent of the air.

Argon makes up just under one percent of the atmosphere and is chemically unreactive, which combination makes it the default choice wherever a process must be kept away from oxygen and nitrogen. Welding shields, metal refining atmospheres and the fill gas in double glazing are all argon for the same reason: it is inert and it is cheap.

It is obtained as a by-product of the cryogenic distillation of air for oxygen and nitrogen, so its supply is effectively unlimited.

Uses

Argon's use is to be present and do nothing. It is the shielding gas for arc welding, keeping oxygen and nitrogen away from the molten weld pool, and the fill gas in double glazing, where it conducts heat less readily than air.

It fills incandescent bulbs to slow filament evaporation, blankets molten metal during casting, and provides the inert atmosphere for growing silicon crystals. Being the cheapest of the noble gases by a wide margin, it is used wherever inertness matters more than any other property.

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 used as

  • Corrosion protection — application · as a shielding gas that keeps oxygen away from hot metal during welding

is produced by

  • Air separation — process · drawn from an intermediate height in the column, between nitrogen and oxygen

is an input to

  • Kroll process — process · the inert atmosphere, without which the titanium would take oxygen from the air

is an alternative to

  • Nitrogen — element · as an inert atmosphere. Nitrogen is far cheaper and not truly inert — it reacts with titanium, magnesium and molten steel — so argon keeps the work where that matters

is found in

  • Air — material · just under one per cent, and almost entirely argon-40 from the decay of potassium in rocks — which is why it is a hundred times commoner than neon despite being heavier

is used in

  • Incandescent lamp — object · the fill gas, which suppresses evaporation from the filament and is why a modern lamp is not a vacuum

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 Argon 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

  • Argon → is produced by (drawn from an intermediate height in the column, between nitrogen and oxygen) → 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

Downstream — what it becomes

  • Argon → is an input to (the inert atmosphere, without which the titanium would take oxygen from the air) → Kroll process → produces (as sponge, which must then be crushed, melted and cast before it is usable metal) → Titanium → is a component of (the other half of the strengthening phase) → Nickel superalloy → is associated with (the jet engine created the industry, because no existing material survived the turbine inlet) → The wartime materials programmes complete chain
  • Argon → is used in (the fill gas, which suppresses evaporation from the filament and is why a modern lamp is not a vacuum) → Incandescent lamp → is used as (and almost all of the energy leaves as heat, which is inherent rather than a design failure and is why it was legislated away) → Lighting
  • Argon → is used as (as a shielding gas that keeps oxygen away from hot metal during welding) → Corrosion protection
  • Argon → is an input to (the inert atmosphere, without which the titanium would take oxygen from the air) → Kroll process → produces (as sponge, which must then be crushed, melted and cast before it is usable metal) → Titanium → is a source for (from the residues of titanium and uranium processing and from bauxite tailings; no deposit is worked for scandium alone) → Scandium → is used as → Alloying
  • Argon → is an input to (the inert atmosphere, without which the titanium would take oxygen from the air) → Kroll process → produces (as sponge, which must then be crushed, melted and cast before it is usable metal) → Titanium → is used as (as titanium dioxide, which consumes more titanium by tonnage than metal production does) → Pigment
  • Argon → is an input to (the inert atmosphere, without which the titanium would take oxygen from the air) → Kroll process → produces (as sponge, which must then be crushed, melted and cast before it is usable metal) → Titanium → is used as (its passive oxide film is why it survives seawater) → Corrosion protection

These are the most distinct paths onward. Argon ends up in others besides.