The war demanded both in Germany and France the sacrifice of all available energy and public spirit; while the Kulturkampf, by bringing into relief the question of the external existence of the Church, thrust all internal dogmatic interests and problems completely into the background.
An electromotive force is therefore set up in this direction, and, if we can calculate the change in available energy due to the processes of the cell, we can foretell the value of the electromotive force.
In the latter case, the tendency of the metal to dissolve in the more dilute solution is greater than its tendency to dissolve in the more concentrated solution, and thus there is a decrease in available energy when metal dissolves in the dilute solution and separates in equivalent quantity from the concentrated solution.
The theoretical form of the freezing point diagrams when solid solutions are present depends on the relation between the available energy and the composition in the two phases.
In accordance with the principles of energetics, any change which involves a decrease in the total available energy of the system will tend to occur, and thus the necessary and sufficient condition for the production of electromotive force is that the available energy of the system should decrease when the current flows.
When a variable quantity is at a minimum a slight change in the system does not affect its value, and therefore, when a solution is saturated, the increase in the available energy of the liquid phase produced by dissolving in it some of the solid must be equal to the decrease in the available energy of the solid phase, caused by the abstraction from the bulk of that part dissolved.
From this and other evidence it has been shown that the first thin shower in open vessels is produced by the accidental presence of tiny crystals obtained from the dust of the air, while the second dense shower marks the point of spontaneous crystallization, where the decrease in total available energy caused by solidification becomes greater than the increase due to the large surface of contact between the liquid and the potentially existing multitudinous small crystals of the shower.
It is necessary to observe that the condition for change in a system is that the total available energy of the whole system should be decreased by the change.
This process involves a decrease in the available energy of the system, for the dissolution of zinc gives out more energy than the separation of copper absorbs.
The available energy A is the amount of external work obtainable by an infinitesimal, reversible change in the system which occurs at a constant temperature T.