[ 189 ] 



VIII. On some Physical Constants of Saturated Solutions. 



By the EARL OF BERKELEY. 

 Communicated by F. H. NEVILLE, F.R.S. 



Received March 28, Read May 19, 1904. 



INTRODUCTION. 



THE following work was undertaken with a view to obtaining data for tlie tentative 

 application of VAN DER WAALS' equation to concentrated solutions. It is evidently 

 probable that if the ordinary gas equation be applicable to dilute solutions, then that 

 of VAN DER WAALS', or one of an analogous form, should apply to concentrated 

 solutions that is, to solutions having large osmotic pressures. 



Saturated solutions were taken for investigation because they presumably have the 

 greatest osmotic pressures, and also because there is reason to believe that, in 

 concentrated solutions at a given temperature, the greater the concentration the less 

 the relative dissociation. For the purpose in view, measurements of volume, pressure 

 and temperature are required. 



Volume. 



This term of the equation is deducible from observations of the density of a 

 saturated solution and of the solubility of the salt at varying temperatures. In 

 Part I., I give the densities and solubilities obtained, together with a description of 

 the methods and apparatus used. 



Pressure. 



I am at present engaged, with the collaboration of Mr. E. G. HARTLEY, in testing a 

 method of directly observing large osmotic pressures. Should the method fail, I 

 propose to determine the vapour pressures of the saturated solutions at different 

 temperatures and from these calculate the corresponding osmotic pressures. The 

 observations and details will be given in Part IT. 



(366.) 20.7.04 



