Determination of Chemical Constants. 13 



The specific heat of cadmium has been measured between 

 17°'l and 92°'2 0. by Gaede {Phys. Z.S. iv. p. 105, 1902); 

 also between -186° and -79° by Behn (Ann. d. Phys. (4) 

 i. p. 257, 1900) *. Employing Graede's results, 



c p = 6-17 at 290°*1 abs., 

 c p = 6-36 at 3G5°'2 abs. 



From Nernst and Lindemann's formula, c v can be cal- 

 culated, viz. : 



? = K(H = °' 509 ; c « = 5 ' 88 - 

 $v _ 147-5 _ q _ , vq 



Putting (> = , v + aT 3 / 2 , 



a L =5'87.10- 5 

 a 2 = 6*44. 10" 5 



Mean . . a — 6*15 . 10~ 5 



Having regard to the need of an approximate figure only, 

 the value G . 10" 5 will be taken, which is approximately the 

 mean between the values 5"93 and 6'15. 



Inserting these values in the vapour-pressure formula (2) 7 

 two equations are obtained from which = 1*65. 



By differentiation, it is found that a change of 2° in the 

 temperature, which is the error in the temperature mea- 

 surements, should lead to a change in the constant of ±0*31, 

 so that the theoretical value 1*47 lies within the experimental 

 error 1-65 ±0*31. 



* Belm deduces from his mean values that 



at 191° abs. C p = 5*844 {.-. 0^=5682), 

 at 87° abs. C p =5'317 (/. C y =5'268). 



[3v in the first case would be 191 and in the second 138 ; it seems 

 advisable therefore to take the value obtained from the melting-point 

 formula: 147 "5. 



