Potassium tree leaves, adding water, heating, and evaporating the solution. When Humphry Davy first isolated the pure element using electrolysis in 1807, he named it "potassium", which he derived from the word potash. The symbol "K" stems from "kali", itself from the root word "alkali", which in turn comes from "" "al-qalyah" "plant ashes." In 1797, the German chemist Martin Klaproth discovered "potash" in the minerals leucite and lepidolite, and realized that "potash" was not a product of plant growth but actually contained a new element, which he proposed to call "kali". In 1807, Humphry Davy produced the element via electrolysis:
Potassium alum a liquid known as "dousa" (), and used as an undercoat for paper sizing. Alum is an ingredient in some recipes for homemade modeling compounds intended for use by children. These are often called "play clay" or "play dough" for their similarity to "Play-Doh". Potassium alum was formerly used as a hardener for photographic emulsions (films and papers), usually as part of the fixer. It has now been replaced in that use by other chemicals. Potassium alum may be a weak irritant to the skin. Potassium alum Potassium alum, potash alum, or potassium aluminium sulfate is a chemical compound: the