A chemical element, symbol Rb, atomic number 37, and atomic weight 85.47. Rubidium is an alkali metal in group 1 of the periodic table. It is a light, low-melting, reactive metal. Little is known about rubidium because it has never been available in quantity at a reasonable price. In 1958 rubidium salts became much more readily available and at lower prices as by-products of lithium chemicals manufacture, and knowledge of the properties and reactions of rubidium metal have developed accordingly. Rubidium was discovered in 1861 by R. Bunsen and G. R. Kirchhoff by interpretation of its spectral lines. Bunsen first prepared free rubidium metal that same year, using an electrolytic method.