Johann Wolfgang Dobereiner (December 13, 1780 - March 24, 1849) was a German chemist. He had little formal schooling, was apprenticed to an apothecary, but attended science lectures and read whatever he could get his hands on. He eventually became a professor at the University of Jena in 1810. In 1829 he discovered trends in certain properties of selected groups of elements. The average atomic mass of lithium and potassium was close to the atomic mass of sodium. A similar pattern was found with calcium, strontium, and barium, with sulfur, selenium, and tellurium, and also with chlorine, bromine, and iodine. The densities for some of these triads followed a similar pattern. These sets of elements became known as "Dobereiner's Triads", one of the forerunners of Mendeleyev's periodic table. He is also remembered for his work on the use of platinum as a catalyst, and for a lighter, known as Dobereiner's lamp in which zinc metal reacted with sulfuric acid to produce hydrogen gas. When the valve was opened, a jet of hydrogen was released and bursts into flame. The ignition was catalyzed by platinum metal. He died in 1849 at the age of 68.