The New Tlieories of Solution. 355 



The mean specific heat between 



20 ° 



and 470° 



is 0-199 



470 



and 750 



is -243 



750 



and 880 



is 'Q26 



880 



and 1190 



is -323. 



As Mr. Fisher was anxious to use our results in some 

 calculations, we supplied him with approximate numbers 

 before all our observations were completed. They do not, 

 however, differ much from the above. 



The general result seems to be that the specific heat of 

 basalt follows the ordinary rule that the specific heat of a 

 substance is greater in the liquid than in the solid state. 

 There is a large absorption of heat in the neighbourhood of 

 800°, which raises the mean specific heat between 750° and 

 880° to the large value of 0*636. 



XLY. The New Tlieories of Solution. 

 By James Walker, B.Sc, Ph.D.,F.R.S.K* 



SINCE the theories of osmotic pressure and of electrolytic 

 dissociation were in 1887 made generally accessible by 

 their publication in the Zeitschrift fur physikalische C hemic, 

 they have in Germany and elsewhere on the Continent enjoyed 

 an ever-increasing favour and popularity. In this country 

 they have mostly been met with a passive resistance ; but in 

 one or two cases where they conflict with rival theories they 

 have encountered active opposition. 



Mr. S. U. Pickering, in particular, has subjected them to 

 unfavourable criticism, in the pages of this Magazine, at the 

 Leeds meeting of the British Association, and elsewhere. 

 His attack is twofold. In the case of osmotic pressure he 

 compares the deductions from theory with the results of 

 experiment, and endeavours to show discordance between 

 them : against the dissociation hypothesis he seeks to raise 

 " theoretical objections of a fundamental character."" 



First, with regard to osmotic pressure, Mr. Pickering 

 singles out the freezing-point of solutions from the many 

 phenomena which have received an explanation from this 

 theory!, as the ground for his attack. The hypothesis of 



* Communicated by the Author. 



t Taking the osmotic-pressure theory in conjunction with his own, 

 Arrhenius (Phil. Mag. xxviii. p. 3(i) enumerates seventeen heads under 

 which these phenomena may be arranged — a number already too small to 

 include the later researches of Nernst and others on solutions. 



2B 2 



