Metallic potassium was first isolated by Sir Humphry Davy in 1807 through the electrolysis of molten caustic potash (KOH). A few months after discovering potassium, Davy used the same method to isolate sodium.

This work led directly to the isolation of sodium and potassium from their compounds (1807) and of the alkaline-earth metals magnesium, calcium, strontium, and barium from their compounds (1808). He also discovered boron (by heating borax with potassium), hydrogen telluride, and hydrogen phosphide (phosphine).

By rubbing two blocks of ice together, Davy showed that friction alone could melt the ice, challenging Lavoisier’s contention that heat was a material substance (“calorique”) and lending support to the modern idea that heat is caused by motion of particles.

Potassium and Sodium Discovered. In 1807, Sir Humphry Davy, the British scientist, tried to prove his idea that potash (potassium hydroxide, KOH) and soda (sodium hydroxide, NaOH) were actually very reactive, oxidized metals. For the experiment, Davy heated potassium hydroxide, on a platinum plate, in a furnace.

Industrial applications for potassium include soaps, detergents, gold mining, dyes, glass production, gunpowder, and batteries.

When potassium is added to water, the metal melts and floats. It moves around very quickly on the surface of the water. The hydrogen ignites instantly. The metal is also set on fire, with sparks and a lilac flame.

While the role of potassium is vital to all plants, it is especially necessary for food crops. Research has shown potassium: Improves water use efficiency. Increases resistance to diseases and insects.

Bananas are rich in the mineral potassium. Potassium helps maintain fluid levels in the body and regulates the movement of nutrients and waste products in and out of cells. Potassium also helps muscles to contract and nerve cells to respond.

Adults should consume about 3,500mg of potassium per day, according to the UK’s National Health Service. The average banana, weighing 125g, contains 450mg of potassium, meaning a healthy person can consume at least seven-and-half bananas before reaching the recommended level.

Juice from potassium-rich fruit is also a good choice:

• Orange juice.
• Tomato juice.
• Prune juice.
• Apricot juice.
• Grapefruit juice.

The following juices are high in potassium, containing the following amounts per cup:

• carrot juice (canned): 689 mg.
• passion fruit juice: 687 mg.
• pomegranate juice: 533 mg.
• orange juice (fresh): 496 mg.
• vegetable juice (canned): 468 mg.
• tangerine juice (fresh): 440 mg.

Topic Overview

Certain dairy products, such as milk and yogurt, are high in potassium (low-fat or fat-free is best)….What yogurt is high in potassium?