Act IV. Internal Energy: the First Paper of Clausius. Entropy: the First Paper of Rankine

Abstract

After quoting Carnot’s claim that to deny the existence of the heat function “would overthrow the whole theory of heat”, Clausius wrote¹:

I am not aware, however, that it has been sufficiently proved by experiment that no loss of heat occurs when work is done; it may, perhaps, on the contrary, be asserted with more correctness that even if such a loss has not been proved directly, it has yet been shown by other facts to be not only admissible, but even highly probable. If it be assumed that heat, like a substance, cannot diminish in quantity, it must also be assumed that it cannot increase. It is, however, almost impossible to explain the heat produced by friction except as an increase in the quantity of heat. The careful investigations of Joule, in which heat is produced in several different ways by the application of mechanical work, have almost certainly proved not only the possibility of increasing the quantity of heat in any circumstances but also the law that the quantity of heat developed is proportional to the work expended in the operation. To this it must be added that other facts have lately become known which support the view, that heat is not a substance, but consists in a motion of the least parts of bodies. If this view is correct, it is admissible to apply to heat the general mechanical principle that a motion may be transformed into work, and in such a manner that the loss of vis viva is proportional to the work accomplished.

Prima che più entre, sappi che se’ nel secondo girone, … e sarai mentre

che tu verrai ne l’orribil sabbione. Però riguarda ben….

Dante, Inferno XIII, 16–20.