On Real and Apparent Freezing-Points. 459 



three, but by a series, of observations, it cannot be too strongly 

 urged that this work should in each case accompany the 

 record of results, when expressed in platinum- temperatures ; 

 aud no one will deny that to have these results expressed at 

 once in terms of the normal air-thermometer will permanently 

 enhance the value of the work in such a manner as to amply 

 recompense the extra labour. With the view of helping 

 towards this desirable end I have endeavoured to show that 

 the simple formula (9) is superior to the joint formulae (3) 

 and (4). 



Peterbouse, Cambridge, 



August 1897. ~\f 1 



LIX. On Heal and Apparent Freezing-Points and the 

 Freezing- Point Methods. By Meyer Wildermann, Ph.D.* 



1. TN the Zeitschrift fur phys. Chem. xv. p. 682, Professor 

 J_ ISTernst gives us a series of interesting considerations 

 from which he further draws the conclusion that the mercury 

 of the thermometer comes to rest, not at the freezing-point T , 

 but at a different temperature t' which he calls the apparent 

 freezing-temperature. Professor Nernst's considerations, 

 which, however, require modification, are of great importance 

 as leading the way to an understanding of the real meaning 

 of an equilibrium at a freezing-temperature. I shall try now 

 to ascertain theoretically the cardinal points upon which a 

 good freezing-point method depends, and to give a theoretical 

 explanation to a series of rules which have previously been 

 found empirically by my late friend P. B. Lewis and myself 

 (Trans. Chem. Soc. 1894 &c.) . 



Before proceeding to the detailed consideration of the pro- 

 cesses which take place between ice and water or solutions, I 

 quote Professor Nernst's views on this point. He writes as 

 follows : — " From researches hitherto made into the pheno- 

 mena of the solution of solid bodies, and especially from the 

 work of Boguskif, we can regard the rate of solution of the 

 solid substance as proportional to the remoteness from the 

 condition of equilibrium ; i. e. since the heat absorbed is 

 proportional to the mass dissolved, we can assume that the 

 change of temperature at any moment is proportional to the 

 said remoteness from the freezing-point." 



* Communicated by tbe Autbor. Part III. of paper communicated 

 to tbe Royal Society, January 13, 1896. See Proceedings of tbe Royal 

 Society, 1896, Zeitschrift fur physik. Chem. (1896), xix. p. 63. 



t On metals in acids. 



V 



