Mikhail Petrovich Avenarius (7.09.1835 — 4.09.1895) was a Russian physicist and a corresponding member of the St Petersburg Academy of Sciences (1876). He was born in Tsarskoye Selo. He graduated from St Petersburg University (1858) and in 1865—90 worked at Kiev University (professor from 1866). He organised the first laboratory of experimental physics in Ukraine and the first practical laboratory course in physics there (1875).His research concerned thermoelectric phenomena and molecular physics. He studied the way the thermoelectromotive force depends on the temperature of the junctions and derived a formula for this dependence (the Avenarius law). He studied the liquid state and vapour under changes of temperature and pressure, and in particular measured the critical temperatures of various liquids. Over the years 1877—86 Avenarius and his pupils obtained critical values for many substances in the Kiev laboratory, and these entered the standard body of physical data and long remained unchanged.