of Zinc, Cadmium, and Mercury. 



4T 



For zinc. X =3*28, instead of 3'12 from the empirical 

 formula. The theoretical formula, therefore, agrees with 

 the observed results remarkably well. 



From the empirical formula for mercury given by Knudsen :: 



\ogp = 10-5724-0-847 log T 



3342-26 



the value of X for the liquid given by the Clausius equation 

 would be 1*51 . 10 4 cals. at the melting-point, where the 

 vapour pressure would become 2*0 . 10~ 6 mm. The latent 

 heat of fusion has been determined by Bridgeman (Amer. 

 Acad. Proc. xlvii. no. 12, pp. 347-438), and at the melting- 

 point the value is 5'6 . 10 2 cals. ; hence the heat of sub- 

 limation of the solid would be 1*57 . 10 4 . If the equation 

 \ T = \ — (C — O p )T were to holdover the range to absolute 

 zero, \ would become 1*61 . 10 4 cals. Inserting the value 

 1*60 in the equation for the vapour pressure and assuming 

 the vapour pressure to be 2*0 . 10~ 6 mm. at the melting-point, 

 the equation 



/>=3-72.I0 tt .T~V 



1/60 . 10* * 



dynes per sq. ci 



is obtained. 



The following table gives the results for these elements,, 

 the first two columns give the value of \ as calculated by 

 Nernst's empirical equation and the corresponding value of 

 the constant K, and the next two columns the values of \ 

 and K obtained from the observations of the vapour pressure, 

 expressed by the equations given above. 





A. 



K. 



V 

 3-28 . 10 4 



K. 



Absolute 

 B.-Pt. 



Absolute 

 M.-Pt. 



Molecular 

 latent heat 

 of Fusion. 



1-82 . 10 3 



Zinc 



Cadmium.. 



3-12 . 10 4 

 2-70 . 10 4 



2-9. 10 13 



1-17. 10 14 



1191° 



691° 



2-63.10 13 



2-77 . 10 4 



5-27. 10' 3 



1051° 



594° 



1-57 . 10 3 



Mercury... 



1-50. 10 4 



4-41. 10 12 



1-60. 10 4 



3-72. 10' 3 



630° 



234°-2 



5-6 . 10* 



* /. e. 



O'AA 



log^=10-4466-|logT-«^~| 



and 



extrapolating- to a value at 0° C. for the vnpour pre? sure of solid mercury, 

 the value would be 2-56 . 10 4 instead of l-8t> . i0 4 for the liquid. 



