Name the author of 1847 review article that conclusively demonstrated the validity of the \"energy concept.\" Please state the \"energy concept\" that developed in Europe during the first half of the 19^th century. Who was the first person to state the First Law in modern mathematical terms AND in what year was his work published? Solution Hermann von Hermholtz was the author of validity of energy concept in 1847. The energy concept in the first half of 19th century, i.e., the first law is the version of law of conservation of energy, which was adopted for thermodynamic systems. It states that total energy of isolated system is constant, energy can neither be created nor destroyed. It is often stated as the change in the internal energy of closed system is equal to the amount of heat supplied to the system, minus the amount of work done by the system on its surroundings and further the impossibility of perpetual motion machines. Rudolf clausius was the first person to state first law in modern mathematical terms and his well esteemed work was published in 1850..