Page:Scientific Papers of Josiah Willard Gibbs.djvu/381

Rh and sometimes cold is produced. When neither is produced, of course the electromotive force of the cell is exactly equal to its diminution of energy per unit of electricity transmitted. But such a coincidence is far less significant than the fact that an absorption of heat has been observed. With acid containing about seven equivalents of water $$(\text{HNO}_{6} + \text{7HO}) [\text{HNO}_{3} + 3\tfrac{1}{2}\text{H}_{2}\text{O}]$$, M. Favre has found and with acid containing about one equivalent of water  In the first example, it will be observed that the quantity of heat absorbed in the cell is not small, and that the electromotive force is nearly one-eighth greater than can be accounted for by the diminution of energy in the cell.

This absorption of heat in the cell he has observed in other cases, in which the chemical processes are much more simple.

For electrodes of cadmium and platinum in hydrochloric acid his experiments give In this case the electromotive force is nearly one-sixth greater than can be accounted for by the diminution of energy in the cell with the work done against the pressure of the atmosphere.

For electrodes of zinc and platinum in the same acid one series of experiments gives and a later series,  In the electrolysis of hydrochloric acid in a cell with a porous partition, he has found