Heats of hydrogenation constitute a body of thermochemical information that has had an on-going significance despite the small number of research groups engaged in the work. Recent highly accurate quantum mechanical calculations requiring reference standards of high accuracy have brought hydrogen thermochemistry back into contemporary focus.This book concentrates on distinctive features of hydrogen thermochemistry such as the practical and historical aspects of experimental determination of the enthalpies of hydrogenation and formation of organic compounds, primarily hydrocarbons, literature on hydrogen thermochemistry over the last 70 years, as well as the impact of contemporary advances in computer hardware and software on the calculation of heats of hydrogenation.