310 THE ROYAL SOCIETY OF CANADA 



phases present, vapour, solid and liquid cyclohexane and liquid SO2 

 the system is invariant, and a further increase in the amount of liquid 

 sulphur dioxide can only cause a change in the relative amounts of 

 the phases. Therefore continued addition of SO2 will cause an increase 

 in the amount of the liquid phase containing excess of SO2, whereas 

 the other liquid phase will gradually disappear. When it has com- 

 pletely disappeared the system will be represented by the point C, 

 where there are again three phases. As the amount of solid cyclo- 

 hexane is diminished the equilibrium temperature will fall until at 

 D the eutetic point is reached. The temperature of the eutetic point 

 is approximately — '72.5°* but the composition of the solution was not 

 accurately determined owing to the fact that the hexamethylene is 

 almost completely insoluble in liquid SO2 at these low temperatures. 

 One part of oil showed no signs of dissolving in 200 parts of SO2 at 

 -72°. 



If the amount of the cyclohexane is diminished still more the 

 temperature rises until at —72.3 the freezing point of pure liquid 

 sulphur dioxide is reached. 



Along line B C there exist four phases, vapour, two liquids and 

 one solid, but if heat be added the solid hexamethylene will dis- 

 appear leaving a univariant system of vapour and two liquids. In 

 general the solubility curve of two partially immiscible liquids is of a 

 somewhat parabolic shape, and it is seen that the curve B F C has the 

 general form of a parabola. Above 13 .6 the critical temperature, the 

 liquids are miscible in all proportions. This curve shows no evidence 

 of any compound formation. 



Chemical Laboratory, 



University of British Columbia, 

 Vancouver, B.C. 



*Obtaineci by extending curve F C to D. 



