Potassium chloride feeds crops, calibrates radiation detectors and once fought fires
Potassium chloride looks and tastes a lot like table salt, and some people sprinkle it on food. But most of it ends up in fields as potash fertiliser, and a trace of natural radioactivity means labs also use it to check that radiation monitors are reading correctly.
Chemically it is a simple pairing of potassium and chlorine, forming clear or white crystals that dissolve easily in water. It occurs naturally as the mineral sylvite, whose name echoes old labels for the salt tied to the name Sylvius, and it is dug from the beds of ancient dried-up lakes. Saskatchewan in Canada alone produced over a quarter of the world's potash in 2017, with Russia and Belarus also major sources.
Farming is its main job. Plants need potassium, alongside nitrogen and phosphorus, for photosynthesis, building proteins and managing water, and growth is often limited by how much they can get. Sold as muriate of potash, potassium chloride dominates the fertiliser market because it is rich in potassium and cheaper than alternatives such as potassium sulfate. It also goes into animal feed, where it happens to raise milk yields.
Its other uses are a grab bag. As a food additive it carries the code E508, and because many people find it bitter or metallic, it is usually blended with ordinary salt, while a pinch of the sweet protein thaumatin tames the aftertaste. It softens household water, serves as a fluid in oil and gas wells, and melts ice in products meant to be gentler on pets and plants. Before the late 1960s, a powder called Super-K put out fires more effectively than baking-soda-based chemicals, until a less corrosive potassium bicarbonate agent replaced it.
Natural potassium contains a sliver of radioactive potassium-40, so the salt gives off beta radiation and faint gamma rays useful for calibrating equipment, including medical scanners. It burns with a lilac flame, forms crystals that cleave neatly in three directions, and once served as infrared lens material, though it slowly absorbs moisture and rots in open air. Heating it with sodium at 850 °C is still the main way to make potassium metal.
Source: Potassium chloride
