| Temperature. | Composition of liquid. | |
| Zinc—cadmium | 264.5° | 73.5 atoms per cent. of cadmium. |
| Zinc—aluminium | 380.5° | 11 ,, ,, aluminium. |
| Copper—silver | 778° | 40 ,, ,, copper. |
The melting points of the pure metals are, zinc, 419°; cadmium, 322°; silver, 960°; copper, 1081°; aluminium, 650°.
2. The two metals can form one or more compounds.
In this case there will be obtained not only the freezing-point curves of the pure metals, but each compound formed will have its own freezing-point curve, exhibiting a point of maximum temperature, and ending on either side in an eutectic point. The simplest curve of this type will be obtained when only one compound is formed, as is the case with mercury and thallium.[[304]] This curve is represented in Fig. 74, where the summit of the intermediate curve corresponds with a composition TlHg2. Similar curves are also given by nickel and tin, by aluminium and silver, and by other metals, the formation of definite compounds between these pairs of metals being thereby indicated.[[305]]
A curve belonging to the same type, but more complicated, is obtained with gold and aluminium;[[306]] in this case, several compounds are formed, some of which have a definite melting point, while others exhibit only a transition point. The chief compound is AuAl2, which has practically the same melting point as pure gold.
3. The two metals form mixed crystals (solid solutions).
The simplest case in which the metals crystallize out together is found in silver and gold.[[307]] The freezing-point curve in this case is an almost straight line joining the freezing points of the pure metals (cf. curve I., Fig. 65, p. [210]). These two metals, therefore, can form an unbroken series of mixed crystals.
In some cases, however, the two metals do not form an unbroken series of mixed crystals. In the case of zinc and silver,[[308]] for example, the addition of silver raises the freezing point of the mixture, until a transition point is reached. This corresponds with curve IV., Fig. 65. Silver and copper, and gold and copper, on the other hand, do not form unbroken series of mixed crystals, but the freezing-point curve exhibits an eutectic point, as in curve V., Fig. 65.