---------------------------------------------------------------------- Molecules of bromo- | | cinnamic aldehyde in | Freezing point. | Deviation from straight 100 mols. of mixture. | | line. ---------------------------------------------------------------------- 0.00 | 31.22° | -- 10.48 | 37.28° | 2.04° 21.91 | 43.12° | 3.50° 30.07 | 46.80° | 4.05° 45.04 | 52.94° | 4.45° 62.16 | 58.82° | 3.77° 82.98 | 65.07° | 2.03° 93.50 | 67.91° | 0.84° 100.00 | 69.56° | -- ---------------------------------------------------------------------- Melting-point Curve.--This curve, like the freezing-point curve, must also be continuous, and the melting points of the different solid solutions will lie between the melting points of the pure components. This is represented by the dotted line in Fig. 49, I. The relative position of the two curves, which can be deduced with the help of thermodynamics and also by experimental determination, is found in all cases to be in accordance with the following rule: At any given temperature, _the concentration of that component by the addition of which the freezing point is depressed, is greater in the liquid than in the solid phase_; or, conversely, _the concentration of that component by the addition of which the freezing point is raised, is greater in the solid than in the liquid phase_. An illustration of this rule is afforded by the two substances chloro- and bromo-cinnamic aldehyde already mentioned. As can be seen from the above table, the addition of chlorocinnamic aldehyde lowers the melting point of the bromo-compound. In accordance with the rule, therefore, the concentration of the chloro-compound in the liquid phase must be greater than in the solid phase; and this was found experimentally. At a temperature of 49.44°, the liquid contained 58.52 per cent., the solid only 52.57 per cent. of the chlorocinnamic aldehyde.