300 



SOME SUGGESTIONS REGARDING SOLUTIONS. 



rei)rcsentiiig' the contimious transition from the gaseous to the licjuid 

 state (see Fhil. Mag., 1887, vol. xxiii, p. 435). It would be interesting 

 to ascertain whether, if concentration be kept constant, osnioti<' i)res- 

 sure woiild also show itself to be a linear function of temperature. 

 But this apart, it appears in the highest degree probable that there 

 should also exist, in theory at least, a continuous transition from solvent 

 to solvent, the representation of which would be a continuous curve. 

 In such a case, on increasing the concentration of the solution by elimi- 

 nating one solvent, the other solvent should not separate visibly, but 

 the two should remain mixed until one solvent has been entirely re- 

 moved. The accomi)anying diagram (Fig, 1) will make this clear. The 



7^ 



O 



Fid. 1. 



sinuous curve A B G D B may represent either continuous change from 

 gas to liquid along an isothermal on decrease of volume, oi' it may 

 represent a similar continuous change from saturated solution to dis- 

 solved sul)stance on increase of concentration. 



.Mr. Aitken's experiments ou the cooling of air containing water- 

 vapor have shown us that it is possible to realize a ]>ortion of tlui curve 

 A B; the x)henomeiion of "boiling with bumping" constitutes a practical 

 rt^alization of a portion of tlie curve J) /:/.• and we may profitably in(|uire 

 what (M»nditions determine sucli unstable states with solvent and sol- 

 vent. 



Kegarding the i)ortion of tlie curve A B, I think that no reasonable 

 doubt can be entertained. It precisely corresponds to the condition of 

 super-saturation. In the liquid-gas curve the volume is decreased at 

 constant temperature without separation of liquid; in the solvent-sol- 

 vent curve the concentration is increased witlumt separation of the 

 solvents. Dr. Nicol has shown that it is possible to dissolve dry sodium 

 sulphate in a saturated solution of sodium sulphate to a very consider- 

 able extent without inducing crystallization] and here we have a reali- 



