Potassium is vital for the proper functioning of the human body. Around 2% of the weight of the Earth's crust is made up of potassium. It is also one of the most abundant elements on the Earth. This metal cannot retain its free form due to its highly-reactive nature. It has to be stored in mineral oil or kerosene, in order to prevent disintegration.
People used to wash wood ash with water, in order to dissolve the potash in it. The water was collected in large iron pots and evaporated to recover a white substance called potash.
The name potash is derived from the pots used for the process and the ash-like residue in it. It was known as vegetable alkali (vegetable refers to plants that give wood and alkali refers to the property of the material). This vegetable alkali was a harsh chemical that was used for cleaning purposes.
At that time, people used a substance called mineral alkali. This was obtained from rocks, and was known as soda ash. Both mineral and vegetable alkali had almost similar properties, and were used for making soap. Nobody could differentiate between vegetable alkali and mineral alkali. For them, the only difference between the two was their sources.
Sir Humphry Davy's Experiments
By the end of the eighteenth century, chemists came to the conclusion that vegetable alkali and mineral alkali contained some elements that they had never seen. They tried various methods to isolate these elements from their compounds.
In 1807, Sir Humphry Davy, a British chemist started working on isolating the elements. He discovered that chemical elements bond together to form compounds, and the bonding is electrical in nature. So he decided to use electricity for splitting elements in chemical compounds. For this purpose, a voltaic battery was used.
He made solutions of potash and soda ash in water, and passed electric current through them. This method did not yield any result, as the elements reacted with water, as soon as they were released from the compound. Hence, Davy could not see any free element as such.
Discovery of Potassium
Soon, Davy realized his folly and decided to exclude water from the experiment. He passed electric current through molten potash, which led to the formation of tiny droplets of a metal, at the negatively charged electrode. He placed the newly discovered metal in water and oil.
While it floated on oil, the metal exploded into a bright lilac flame, as it reacted with water. In hydrochloric acid, the metal produced a red flame. Sir Humphry Davy named it potassium. This feat was achieved in England, on October 6, 1807. A few days later, he discovered sodium using the same method.
Now, it is a known fact that the alkali extracted from wood ash, termed as potash by our ancestors, was actually potassium carbonate. Similarly, the compound known as soda ash was sodium carbonate.
Earlier, people used to cut down trees in large numbers and burn them to produce wood ash, which in turn, was used for making potash. Now, potassium is produced through electrolysis of its hydroxides or through thermal methods. The compounds of this metal are found abundantly in the deposits formed by evaporation of water in ancient lakes and seabed.
Potash is mined from Saskatchewan in Canada, Germany, and three states in the U.S. - California, New Mexico, and Utah. Pure potassium is very soft and is silvery gray in color. Though the metal is non-toxic, anybody handling the pure form of potassium should take sufficient precautions to ensure safety, as it is highly reactive.