Wojciech Alojzy Świętosławski (1881 – 1968) was a Polish physical chemist, who is considered the "father of modern thermochemistry". He developed a static method of cryometric measurement and a new method of testing coal. Świętosławski was Vice-Chairman of the International Union of Pure and Applied Chemistry (IUPAC) and created the foundations for a new branch of physical chemistry: polyazeotropy. In 1933 he became a member of the Temporary Scientific and Advisory Committee Early Years Świętosławski was born on 21 June 1881 in the village of Kiryjowka, Podolian Governorate, Russian Empire. He spent his early years in Kiev, where he graduated from high school (1899). In 1906, he graduated with an engineering degree at Chemistry Department of Kiev Technical University. His first research paper, "Thermochemical Analysis of Organic Compounds" was published in 1908, in "Polish Yearly Magazine ("Rocznik Polski"). In appreciation of his work, Świętosławski was awarded the Mendeleyev Award by Russian Scientific Association. In the 1910s, Świętosławski went to Moscow, where he took a job at Chemical Laboratory of Moscow University. In 1917 he completed his thesis, writing about oxymes. In the mid-, and late 1910, Świętosławski remained in Moscow, working, among others, on Aromatic hydrocarbon, Nitric acid, Nitro compound, Amine, and burning in bomb calorimeters. Interwar Poland In 1918 Świętosławski returned to Poland, leaving his laboratory in Moscow and urging other highly qualified Polish scientists to follow him. In 1919, he was named Professor of Physical Chemistry at Warsaw University of Technology, and returned to scientific research, working on enthalpy of vaporization. In 1920, at the Conference of International Chemical Union in Rome, he made a motion to accept benzoic acid as an international standard of marking the bomb calorimeters. In 1922, his motion was accepted, and Świętosławski was named head of the Thermochemical Data Commission, which coordinated research on marking the heat of combustion. In the early 1920s, Świętosławski developed a new direction in the calorimetrical research, which he called microcalorimetry. He constructed microcalorimeters, which worked in isometric and adiabatic conditions as well as microcalomieters based on partial heat exchange with the surroundings. Due to his research, it became possible, among others, to mark the value of radiation of uranium aperture. Later on, he worked on measuring of Vapor pressure and boiling temperature. Furthermore, he constructed the ebulliometer. In 1928, Świętosławski was named deputy chairman of International Chemical Union. In 1934 he was appointed chairman of Commission of