Skip to content
Material World
Element · K

Potassium

The third of the three elements every fertiliser is measured by, mined as ancient evaporated seawater.

Agricultural input

Potassium is essential to plants and is the K in the N-P-K rating printed on every bag of fertiliser. It is mined as potash — chiefly sylvite and carnallite — from bedded salt deposits left by seas that evaporated hundreds of millions of years ago.

As a metal it is even more reactive than sodium, and like sodium it is essentially never encountered in elemental form outside industry.

Uses

Potassium is the third of the three fertiliser elements, alongside nitrogen and phosphorus, and that is where nearly all of it goes. Potash is mined and spread with relatively little chemical processing in between.

Smaller uses follow from its chemistry: potassium hydroxide makes soft soaps, potassium nitrate is a component of black powder and a food preservative, and potassium compounds are used in glassmaking where a harder, more brilliant glass than the sodium equivalent is wanted.

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

  • Fertiliser — application · the K in N-P-K, mined as potash

is found in

is extracted from

  • Sylvite — mineral · essentially the world's only source of agricultural potassium Wikidata

is produced by

  • Molten salt electrolysis — process · difficult even electrolytically, because the metal dissolves in its own molten salt
  • Brine evaporation — process · from potash brines, where the potassium salts are among the last to crystallise and so the last ponds in a series

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 Potassium 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

  • Potassium → is produced by (from potash brines, where the potassium salts are among the last to crystallise and so the last ponds in a series) → Brine evaporation → takes as input (and the pond sequence is run so that the less soluble salts crystallise out first, leaving the sodium chloride to be harvested on its own) → Salt → is sourced from (mined as rock salt from bedded deposits, or dissolved in place and pumped up as brine — which is what the chemical industry wants anyway) → Evaporite → is sourced from (what is left when a body of seawater evaporates faster than it is replenished — the salts come out in order of solubility, which is why the sequence is readable) → Seawater → is composed of (about 96.5 per cent by mass — seawater is 3.5 per cent dissolved solids and the rest of it is this) → Water
  • Potassium → is produced by (difficult even electrolytically, because the metal dissolves in its own molten salt) → Molten salt electrolysis → takes as input (after concentration, as one of the two routes to lithium chloride) → Lepidolite
  • Potassium → is extracted from (essentially the world's only source of agricultural potassium) → Sylvite
  • Potassium → is produced by (from potash brines, where the potassium salts are among the last to crystallise and so the last ponds in a series) → Brine evaporation → takes as input (the feedstock for solar salt and, in the salars, for the far stronger brines that lithium comes from) → Seawater → is composed of (about 96.5 per cent by mass — seawater is 3.5 per cent dissolved solids and the rest of it is this) → Water
  • Potassium → is produced by (from potash brines, where the potassium salts are among the last to crystallise and so the last ponds in a series) → Brine evaporation → takes as input (and the pond sequence is run so that the less soluble salts crystallise out first, leaving the sodium chloride to be harvested on its own) → Salt → is sourced from (by solar evaporation, which needs a dry sunny coast and is the cheapest route there is) → Seawater → is composed of (about 96.5 per cent by mass — seawater is 3.5 per cent dissolved solids and the rest of it is this) → Water
  • Potassium → is produced by (from potash brines, where the potassium salts are among the last to crystallise and so the last ponds in a series) → Brine evaporation → takes as input (and the pond sequence is run so that the less soluble salts crystallise out first, leaving the sodium chloride to be harvested on its own) → Salt → is sourced from (mined as rock salt from bedded deposits, or dissolved in place and pumped up as brine — which is what the chemical industry wants anyway) → Evaporite → is composed of (precipitated early, when the water has reduced to roughly a fifth of its volume) → Gypsum

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

Downstream — what it becomes