Potassium - Element information, properties and uses (2024)

Transcript :

Chemistry in its element: potassium

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You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.

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Chris Smith

Hello, this week the story of the first alkaline metal ever isolated, why it's an alkaline metal at all and why its symbol begins with the letter K. Here's Peter Wothers.

Peter Wothers

Potassium - the only element named after a cooking utensil. It was named in 1807 by Humphry Davy after the compound from which he isolated the metal, potash, or potassium hydroxide.

An extract from the 1730s by the Dutch chemist Herman Boerhaave describes how potash got its name:

"Potas or Pot-ashes is brought yearly by the Merchant's Ships in great abundance from Coerland (now part of Latvia and Lithuania), Russia, and Poland. It is prepared there from the Wood of green Fir, Pine, Oak, and the like, of which they make large piles in proper Trenches, and burn them till they are reduced to Ashes... These ashes are then dissolved in boiling Water, and when the Liquor at top, which contains the Salt, is depurated, i.e. freed from impurities, by standing quiet, it is poured off clear. This, then, is immediately put into large copper Pots, and is there boiled for the space of three days, by which means they procure the Salt they call Potas, (which signifies Pot-Ashes) on account of its being thus made in Pots.

Even earlier in the 16th Century, Conrad Gesner tells us that "Of the hearbe called Kali, doe certayne prepare a Salt"

He describes this plant, Kali whose Latin name is Salsola kali but is more commonly known as Saltwort:

"Kali is of two Cubites of heygth, hauing no prickles or thornes, & is sometymes very red, saltye in taste, with a certayne vngratefull smell, found & gathered in saltie places: out of which, the Salt of Alkali maye be purchased"

His method of production of this Salt of Alkali is pretty similar to that described by Boerhaave with both processes actually yielding an impure mixture of what we would now call potassium and sodium carbonate; the wood ash method yielding more potassium carbonate, potash, the salty herbs giving more sodium carbonate, soda. However, it is from the herb kali, that we owe the word that describes both - al-kali or alkali; the 'al' prefix simply being Arabic definite article 'the'.

The crude potash can be made more caustic or 'pure' by treating a solution of it with lime water, calcium hydroxide. The potassium carbonate and calcium hydroxide solutions react with a bit of chemical partner-swapping: insoluble calcium carbonate or chalk precipitates out, leaving a solution of potassium hydroxide. It was from this pure hydroxide that Davy first isolated the metal potassium. To do this he used the relatively new force of electricity.

After unsuccessfully trying to electrolyse aqueous solutions of potash, during which he only succeeded in breaking apart the water, he reasoned that he needed to do away with the water and try to electrolyse molten potassium hydroxide. This he did on the sixth of October, 1807 using the large Voltaic pile he had built at the Royal Institute in London. His younger cousin, Edmund Davy, was assisting Humphry at the time and he relates how when Humphry first saw "the minute globules of potassium burst through the crust of potash, and take fire as they entered the atmosphere, he could not contain his joy".

Davy had every right to be delighted with this amazing new metal: it looked just like other bright, shiny metals but its density was less than that of water. This meant the metal would float on water --at least, it would do if it didn't explode as soon as it came into contact with the water. Potassium is so reactive , it will even react and burn a hole through ice. This was the first alkali metal to be isolated, but Davy went on to isolate sodium, calcium, magnesium and barium.

Whilst Davy named his new metal potassium after the potash, Berzelius, the Swedish chemist who invented the international system of chemical symbols now used by chemists the world over, preferred the name kalium for the metal, better reflecting its true origins, he thought. Hence it is due a small salty herb that we now end up with the symbol K for the element pot-ash-ium, potassium.

Chris Smith

Cambridge chemist Peter Wothers. Next time beautiful but deadly is the name of the game.

Bea Perks

Arsenic gets its name from a Persian word for the yellow pigment now known as orpiment. For keen lexicographers apparently the Persian word in question Zarnikh was subsequently borrowed by the Greeks for their word arsenikon which means masculine or potent. On the pigment front, Napoleon's wallpaper just before his death is reported to have incorporated a so called Scheele's green which exuded an arsenic vapour when it got damp.

Chris Smith

So potent or not, licking the wallpaper in Napoleon's apartments is definitely off the menu. That's Bea Perks who will be with us next time to tell us the deadly tale of arsenic, I hope you can join us. I'm Chris Smith, thank you for listening and goodbye.

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Chemistry in its element is brought to you by the Royal Society of Chemistry and produced bythenakedscientists.com. There's more information and other episodes of Chemistry in its element on our website atchemistryworld.org/elements.

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Potassium
    - Element information, properties and uses (2024)

FAQs

Potassium - Element information, properties and uses? ›

A soft, silvery metal that tarnishes in air within minutes. The greatest demand for potassium compounds is in fertilisers. Many other potassium salts are of great importance, including the nitrate, carbonate, chloride, bromide, cyanide and sulfate. Potassium carbonate is used in the manufacture of glass.

What are the properties of the element potassium? ›

Potassium metal is soft and white with a silvery lustre, has a low melting point, and is a good conductor of heat and electricity. Potassium imparts a lavender colour to a flame, and its vapour is green. It is the seventh most abundant element in Earth's crust, constituting 2.6 percent of its mass.

What are some uses for potassium? ›

It helps your nerves to function and muscles to contract. It helps your heartbeat stay regular. It also helps move nutrients into cells and waste products out of cells. A diet rich in potassium helps to offset some of sodium's harmful effects on blood pressure.

What are some fun facts about the element potassium? ›

Potassium was first purified in 1807 by Cornish chemist Humphry Davy (1778–1829) from caustic potash (KOH) via electrolysis. Potassium was the first metal to be isolated using electrolysis. Potassium compounds emit a lilac or violet flame color when burned. It burns in water, just like sodium.

What is the summary of potassium? ›

It is a soft, silvery white metal, not found free in nature and rarely used as the metal (except as a chemical reagent) because of its extreme reactivity. Potassium is essential for life and is present in all soils.

What are the bad properties of potassium? ›

Contact with solid Potassium can cause severe burns. * Exposure to Potassium fumes can irritate the nose, throat and lungs with sneezing and coughing. * Prolonged exposure to Potassium fumes can cause sores of the inner nose. * Potassium is a FLAMMABLE and REACTIVE chemical and a FIRE and EXPLOSION HAZARD.

What is potassium in everyday use? ›

It has a wide role in the industrial sector for manufacturing soaps and dyes. Potassium is used to prepare medicines as it balance and fluid, prevent the formation of stone in the kidney. Thus, they are also used as supplements.

What is the daily use of potassium? ›

An adequate intake of potassium is 3,400 milligrams (mg) per day for healthy adult males and 2,600 mg per day for healthy adult females. The table below shows specific recommendations for different age groups. The adequate intake during pregnancy is 2,900 mg, and it is 2,800 mg while breastfeeding or chestfeeding.

What is the largest use of potassium? ›

Economically important potash minerals include: Carnallite, Sylvite and Sylvinite. Potassium has many essential biological roles in animals, plants and humans, such as metabolism and growth. Hence the main application of potash is in the manufacture of fertilisers.

What is the most important thing about potassium? ›

Potassium is a mineral that is essential for all of the body's functions. It helps your nerves, muscles and heart to function well, and also helps move nutrients and waste around your body's cells.

What is potassium info for kids? ›

Potassium reacts readily with the oxygen in air, producing a lavender flame and forming an oxide compound. Potassium reacts violently with water, yielding potassium hydroxide (KOH) and hydrogen gas (which ignites). Because of its high reactivity, potassium is stored submerged in mineral oil.

What is the element potassium used for? ›

What are the industrial uses of potassium? Industrial applications for potassium include soaps, detergents, gold mining, dyes, glass production, gunpowder, and batteries. Potassium also plays a vital role in our bodies.

What best describes potassium? ›

A soft, silvery metal that tarnishes in air within minutes. The greatest demand for potassium compounds is in fertilisers. Many other potassium salts are of great importance, including the nitrate, carbonate, chloride, bromide, cyanide and sulfate.

What does potassium tell us? ›

Your provider may order this test if you have signs of high blood pressure or heart problems. Small changes in potassium levels can have a big effect on the activity of nerves and muscles, especially the heart. Low levels of potassium can lead to an irregular heartbeat or other electrical malfunction of the heart.

What are the properties of potassium for kids? ›

It is a soft, white metal with a silvery luster. Its physical properties are similar to those of the other alkali metals—it is highly malleable and ductile and a good conductor of both heat and electricity, with a low melting point (145.90 °F, or 63.28 °C). The boiling point of potassium is (1,400 °F, or 760 °C).

What are the properties of each element? ›

Atomic properties that are critical to the behavior of elements are electron configuration, atomic size, ionization energy, electron affinity, and electronegativity. The electron configuration (nl#: spdf notation) gives the distribution of electrons in principal energy levels and sublevels of an atom.

What are 4 properties of potassium chloride? ›

Chemical and physical properties

It is odourless and has a slightly sour taste. The melting point is 770 °C (1,418 °F), and the boiling point is 1,420 °C (2,588 °F). Potassium chloride readily dissolves in water, and the aqueous solution that forms is a good conductor of electricity.

Is potassium a metal or metal? ›

Potassium is the seventh most abundant metal in the Earth's crust. It makes up 2.4% by mass.

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