Discovery of Potassium
In 1806 English chemist Sir Humphry Davy discovered that chemical bonding was electrical in nature and that he could use electricity to split substances into their basic building blocks – the chemical elements.
In 1807 he isolated potassium for the first time at the Royal Institution, London. He electrolyzed dried potassium hydroxide (potash) which he had very slightly moistened by exposing it to the moist air in his laboratory. The electrolysis was powered by the combined output of three large batteries he had built.
When he applied a voltage from his batteries to the potassium hydroxide, he found globules “having a high metallic lustre” collected at the negatively charged electrode.
Edmund Davy, who assisted in the experiment, described Sir Humphry Davy’s reaction to the production of potassium metal, his Eureka moment:
“… when 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 – he actually danced about the room in ecstatic delight; some little time was required for him to compose himself sufficiently to continue the experiment.”
Potassium was the first metal to be isolated by electrolysis.
Davy was astonished at the new metal’s low density, observing that it floated on oil – something no other metal would do. He placed a piece of potassium in water and observed that the water, “decomposes it with great violence, an instantaneous explosion with brilliant flame. He also (bravely) added potassium to hydrochloric acid and saw it burn with a bright red flame.
The name potassium is from the English word ‘potash’, originally meaning an alkali extracted with water in a pot of ash of burned wood or tree leaves.
Potassium’s symbol K comes from ‘kalium’ the name of the element in Germany and Scandinavia.
Just a few days after isolating potassium, Davy isolatedsodium for the first time using the same method.
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