Solubility of Liquids in Water

Solubility of Liquids in Water can occur in all proportions without separating out into two phases. Such is the case with methyl and ethyl alcohols, and it is easy to pass from what may be termed a solution of alcohol in water, by successive additions of alcohol, to a solution of water in alcohol, the latter liquid being so much in excess as to merit the term solvent, the water being the solute.

Solubility curves for water and phenol.

The majority of liquids, however, do not mix in all proportions with water at the ordinary temperature. When phenol is added to water, two layers are produced; the upper one consisting of a solution of phenol in water; the lower, of water in phenol. On gently warming and shaking the liquid becomes opalescent at about 68° C., and at 68.3° C. - the critical solution temperature - the two liquids become entirely miscible. This is shown in Fig.

It will be observed that, as with gases, Solubility of Liquids in Water of the three foregoing liquids in water fall with rise of temperature, although the solubilities of water in these liquids rises with temperature. Rex has made the interesting observation in connection with a considerable number of liquids that the value for k, in Winkler's formula for gases given above, increases regularly with the molecular weight in the case of such substances as contain a given number of atoms; it also increases with the temperature. There is thus a close analogy between the solubilities of neutral liquids in water and the absorption of neutral gases by water.

The solubility of water in benzene is as follows:

Temperature, °C.	3	23	40	55	66	77
	0.030	0.061	0.114	0.184	0.255	0.337

The steady rise in solubility is noteworthy.