│Robert Wilhelm Bunsen│ was born at Göttingen on March 31, 1811, and after studying chemistry under Stromeyer, the discoverer of cadmium, went to Paris and worked with Gay Lussac. In 1836 he succeeded Wöhler as teacher of chemistry in the Polytechnic School of Cassel, and in 1842 became Professor of Chemistry in the University of Marburg. In 1852 he was called to Heidelberg, and occupied the Chair of Chemistry there until his retirement in 1889. He died at Heidelberg on August 16, 1899. [Illustration: BUNSEN, KIRCHHOFF, AND ROSCOE.] Bunsen first distinguished himself by his classical work on the _cacodyl compounds_, obtained as the result of an inquiry into the nature of the so-called “fuming liquor of Cadet,” an evil-smelling, highly poisonous, inflammable liquid formed by heating arsenious oxide with an alkaline acetate. The investigation (1837–1845) is noteworthy, not only for the skill it exhibits in dealing with a difficult and highly dangerous manipulative problem, but also for the remarkable nature of its results and on account of their influence on contemporary chemical theory. The research, in the words of Berzelius, was the foundation-stone of the theory of compound radicals. The name _cacodyl_ or _kakodyl_ was suggested by Berzelius in allusion to the nauseous smell of the compounds of the new radical _arsinedimethyl, As (CH3)2_, as it was subsequently termed by Kolbe. Bunsen greatly improved the methods of gasometric analysis; these he applied, in conjunction with Playfair, to an examination of the gaseous products of the blast furnace in the manufacture of iron, and thereby demonstrated the enormous waste of energy occasioned by allowing the gases to escape unused into the air, as was then the universal practice. This inquiry effected a revolution in the manufacture of iron as important, indeed, as that due to the introduction of the hot blast.