Determination of Chemical Constants. 



-Now, /-it /*T /»T 



A T =\ +4 C p dT-\ <--;dt-f m -\ C l p dT; 



Jo Jo J'?m 



where C p = atomic heat of vapour, 

 g« = ,, „ solid, 



iquid, 



f m — latent heat of fusion at melting-point. 

 Whence 



X » = *J_4-963T + [~ ^°] T + /;„ + <; ( T-T,„) + % a T* 



where | — ^= can be obtained from the tables of the 



integration of Debye's formula for c v (Berl. Ber. lii. 

 p. 1176, 1912), a is the empirical constant for conversion 

 of c v to c p , and c p is considered to be constant. 



In the case of mercury, from specific heat measurements 

 (Koref, Ann. d. Pliys. xxxvi. p. 64, 1911; and Pollitzer, 

 Zeit. Elektr. Chem. xix. 1912), ^=97 ; .-. /3v/T m =0-4142. 



and Uw ~ U ° = 5-063. 



f m = 555 (Pollitzer) 



549 (Bridgman. Proc. Am. Acad, xlvii. 



■ p. 319 et sec/., 19.11) 



Mean = 552 



* a = 21 . 10~ 5 (from Pollitzer's measurements of 



specilic heat). 



Thus 



A s = \t-4-963T + ^(T-TJ + 1190-5 + 552 + 705 

 =Xrf~4-963T + cj(T-T m ) + 1813. 



* As the coefficient of expansion of the solid = O00014 at the 

 melting-point (Bridgman, /. c), and v m = 14*90 (density 13-46, Bridgman, 



I.e.), and as -=21.10~ 3 T 3/2 , the compressibility of the solid (k) s 



would be 2-17 Xl0 -6 per kg./cm. 2 (which lies between the values 

 l - 66. 10~ 6 for zinc and 2*3 . 10 -6 for cadmium). The compressibility 

 of the liquid at 0° C. is 3*90 . 10 -6 per kg./cm. 2 , and the coefficient of 

 expansion is 0*00018 and v= 14*71, whence a (liquid) would become 

 17-35. 10 -5 . Cj,— C z r Las been determined at 0°C. by Bridgman 

 = 0*805, whence a would be 17*85. 10~\ 



