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:  This test was invented by the German Chemist, Julius Robert Von Mayer (1814–1878). Julius von Mayer:  He is best known for enunciating in 1841 one of the original statements of the conservation of energy or what is now known as one of the first versions of the first law of thermodynamics, namely that "energy can be neither created nor destroyed".
energy can be neither created nor destroyed