In Stockholm, Arfwedson knew the chemist Jöns Jakob Berzelius and received access to his private laboratory, where he discovered the element lithium in 1817, during analysis of the mineral petalite. The actual isolation of lithium metal would be done by others, lithium is a very dangerous alkali metal since it is very flammable and reactive and stored it in natural oil. It is a soft silvery metal. Under standard conditions it is the lightest metal and the lightest solid element.