The principles of thermochemistry are applied for this process. His most famous paper, outlining his law on thermochemistry, was published there in 1840. Several thermodynamic definitions are very useful in thermochemistry. This type of reaction is often used as a hypothetical reaction in thermochemistry. His experimental work in thermochemistry was summarised in a doctorate thesis. In 1890, Beketov delivered lectures on the "Basics of Thermochemistry" at Moscow State University. Thermochemistry is concerned with the changes in internal energy, principally as heat, in chemical reactions.