The inventor of Mayer's reagent and one of the founders of thermodynamics, Julius von Mayer was the first to enunciate what phrase, known as the first law of thermodynamics?
Mayer's reagent Mayer's reagent is an alkaloidal precipitating reagent used for the detection of alkaloids in natural products. Mayer’s reagent is freshly prepared by dissolving a mixture of mercuric chloride (1.36 g) and of potassium iodide (5.00 g) in water (100.0 ml). Most alkaloids are precipitated from neutral or slightly acidic solution by Mayer’s reagent (potassiomercuric iodide solution) to give a cream coloured precipitate. This test was invented by the German Chemist, Julius Robert Von Mayer (1814–1878).
Theory of heat In the history of science, the theory of heat or mechanical theory of heat was a theory, introduced in 1798 by Sir Benjamin Thompson (better known as 'Count Rumford'), and developed more thoroughly in 1824 by the French physicist Sadi Carnot, that heat and mechanical work are equivalent. It is related to the mechanical equivalent of heat. Over the next century, with the introduction of the second law of thermodynamics in 1850 by Rudolf Clausius, this theory evolved into the science of thermodynamics. In 1851, in his "On the Dynamical Theory of Heat", William Thomson outlined the view, as based on recent experiments by those such as James Joule, that “heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect.”