Potassium

Potassium was first prepared in pure form in 1807 by English chemist Sir Humphry Davy (1778-1829). Davy used a new method of isolating elements that he had invented, electrolysis. In electrolysis,an electric current is passed through a molten (melted) compound. The electrical current breaks the compound into its elements.

Discovery and naming: Early humans were familiar with potash, apotassium compound that forms when wood burns. Wood ashes were washed with water to dissolve the potash. It was then recovered by evaporating the water. Potash was often called vegetable alkali. That namecomes from the origin of the material ("vegetable" plants that contain wood) and the most important property of the material, alkali. The word alkali means a strong, harsh chemical that can be used forcleaning. Common household lye (such as Drano) is a typical alkali. The chemical name for potash is potassium carbonate (K 2 CO 3 ). Early humans also knew about a similar substance called mineralalkali. This material was made from certain kinds of rocks. But it also had alkali properties. "Mineral alkali" was also called soda ash. The modern chemical name for soda ash is sodium carbonate(Na 2 CO 3). For many centuries, people had trouble telling "vegetable alkali" and "mineral alkali" apart. The two materials looked and acted very much alike. For example, they could both be used as cleaningmaterials. The main difference between them was the source from which they came. It was not until the eighteenth century that chemists understood the difference between potash (vegetable alkali) andsoda ash (mineral alkali). By the late 1700s, chemists were reasonably sure that both potash and soda ash contained elements they had never seen. They tried to think of ways to break these compoundsdown into their elements. The first method that Davy tried was to pass an electric current through a water solution of one compound or the other. But no new element was ever formed. What Davy did...