M.Le Chatelier, M.Charpy, M.Dumas, M.
Osmond, in France; Sir W.Roberts Austen and Mr.Stansfield, in England, have given manifold examples of the fertility of these methods.

The question, moreover, has had a new light thrown upon it by the application of the principles of thermodynamics and of the phase rule.
Alloys are generally known in the two states of solid and liquid.
Fused alloys consist of one or several solutions of the component metals and of a certain number of definite combinations.

Their composition may thus be very complex: but Gibbs' rule gives us at once important information on the point, since it indicates that there cannot exist, in general, more than two distinct solutions in an alloy of two metals.
Solid alloys may be classed like liquid ones.

Two metals or more dissolve one into the other, and form a solid solution quite analogous to the liquid solution.

But the study of these solid solutions is rendered singularly difficult by the fact that the equilibrium so rapidly reached in the case of liquids in this case takes days and, in certain cases, perhaps even centuries to become established..