Potassium Potassium Potassium is a chemical element with symbol K (from Neo-Latin "kalium") and atomic number 19. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals. All of the alkali metals have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge – a cation, which combines with anions to form salts. Potassium in nature occurs only in ionic salts. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air
Potassium ferrioxalate Potassium ferrioxalate Potassium ferrioxalate, also known as potassium trisoxalatoferrate(III), is a chemical compound with the formula [], where iron is in the +3 oxidation state. It is an octahedral transition metal complex in which three bidentate oxalate ions are bound to an iron center. Potassium acts as a counterion, balancing the −3 charge of the complex. Crystals of the trihydrated form of the complex, []·3, are emerald green in color. In solution, the salt dissociates to give the ferrioxalate anion, [], which appears fluorescent green in color. Potassium ferrioxalate is often used in chemical actinometry, i.e. the measure of light