Dmitri Mendeleev became a Doctor of Science in 1865. He earned the degree after defending his dissertation, “On the Combinations of Water with Alcohol,” a study of how mixtures of water and alcohol behave at different concentrations and temperatures.
The doctorate marked an important stage in Mendeleev’s academic career. He had already studied chemistry and published research, but the 1865 qualification strengthened his position in Russian higher education. He later became a professor at the University of Saint Petersburg, where he developed much of the work that made him famous.
Mendeleev’s periodic table followed in 1869, four years after the doctorate. He arranged elements according to their properties and atomic weights, leaving gaps for substances not yet discovered. Those predictions were later supported by the discoveries of gallium, scandium and germanium.
A common mix-up is to associate 1865 with the periodic table itself. The degree came first; the landmark periodic-table presentation occurred in 1869.