Portrait of Antoine Lavoisier (1743-1794) with his wife Marie, after an oil painting of 1788 by David. Lavoisier was instrumental in the use of accurate measurement in chemistry for the study of the composition of materials, oxidation and other combustion reactions. It was Lavoisier who correctly deduced the contribution of oxygen in the air to combustion, and that air consisted of oxygen and nitrogen. His book Methods of Chemical Nomenclature" of 1787 set the method of naming substances by their composition of elements which is still used today. Lavoisier was guillotined by French revolutionary radicals in 1794 on farcical charges made by his life-long rival Marat."