(5) If we might also regard the couple as a reversible thermodynamic engine for converting heat into work, and might neglect irreversible effects, such as conduction, which are independent of the current, we should expect to find the ratio of the heat absorbed at the hot junction to the heat evolved at the cold junction, namely, PIP', to be the same as the ratio T/T of the absolute temperatures of the junctions.
An irreversible process which permits a more complete experimental investigation is the steady flow of a fluid in a tube already referred to in section to.
Dolezalek, however, has attributed the difference to mechanical hindrances, which prevent the equalization of acid concentration in the neighbourhood of the electrodes, rather than to any essentially irreversible chemical action.
But apart from the fact that the authority of the Privy Council, as not being a "spiritual" court, is denied by many of the clergy, no one claims that its decisions are irreversible in the light of fresh evidence.
A common illustration of an irreversible process is the expansion of a gas into a vacuum or against a pressure less than its own.