Manfred Eigen (1927- present) was awarded half of the 1967 Nobel Prize in Chemistry for his work on extremely rapid chemical reactions. He invented “relaxation techniques” to study these reactions. The techniques involve the application of bursts of energy to a solution that briefly destroys its equilibrium. Eigen studied what happened to the solution in the extremely brief interval between the destruction of the equilibrium and the establishment of a new equilibrium, using absorption spectroscopy – a technique for determining the structure of a substance by measuring the intensity of radiation it absorbs. Among specific topics he investigated were the rate of hydrogen ion formation through water dissociation, diffusion-controlled protolytic reactions (in which an acid and base are both spreading and reacting by exchanging protons and producing another acid and base), and the kinetics of keto-enol tautomerism (chemical equilibrium between a ketone or an aldehyde and an enol).