Date of Birth: 08/07/1802
Place of birth: Geneva
Russian chemist, academician of the Petersburg Academy of Sciences (since 1830). He was born in Geneva. He graduated from the University of Dorpat (MD, 1825).
Improve education at Stockholm University (1825). Since 1830 - Professor of the St. Petersburg Institute of Technology, in 1832-1849 gg. - St. Petersburg Mining Institute.
One of the founders of the thermochemistry. Much earlier X. Thomsen and Berthelot, P. put forward (1840) the position, according to which the value of the thermal effects of the reaction may serve as a measure of chemical affinity. He opened (1840) the basic law of thermochemistry - the law of the constancy of the amount of heat in which the heat of reaction depends only on the initial and final states of the reactants and not on the number of process steps (Law of Hess).
He proved (1842) that the mixing of neutral salt solutions is no thermal effect (usually thermoneutral). I found that in the neutralization of 1 mole equivalent of any strong acid with a strong base is always the same amount of heat is released (13.5 kcal). He opened and determined the composition of the four new minerals (1830-1834 gg.) - Vertita, uvarovite, gidroboratsita and folbortita. Offered (1833) a method of producing tellurium silver telluride - a mineral that was first studied them.
Studied (1832) okislykobalta. Established catalyzing and adsorption properties of finely divided platinum. One of the first studied the composition of the Caucasian oil. Opened sugar acid.
Posted textbook "Foundations of pure chemistry" (1831), which went through seven editions.
In his honor, called the silver telluride hessite.
According to the materials of a biographical directory "outstanding chemists of the world" (authors VA Volkov et al.) - Moscow, "High School" 1991