al 
( 341 ) 
The second determination gave = — 4212 cal. 
As the mean of the two experiments we will take 
— 4215 eal. (at 39°) 
whilst THOMSEN gives — 4260 ea]. (at 18°) 
Pf. Determination of the heat of solution of the system formed 
from Zn SO,.7H,O — ZnSO, .400 HO (at 39°). 
in SO. CHO used 20.366 er. 
Water value of calorimeter ete. = 530 er. 
ty = 16.232 At = — 0.069 
; 287.44 
Heat of solution = ——____ X 530 X — 0.069 X 0.970 = — 500 cal. 
20.566 
A second determination gave — 516 cal. 
As mean we will take — 508 cal. 
From the determinations described under @ and (2 that heat of 
fusion of Zn SO4,.7 H20 is therefore — 3752 cal. (39°), whilst from 
THOMSEN’s figures we obtained, by extrapolation, — 3609 cal. (18°). 
The agreement is satisfactory when it is considered that similar 
and even greater differences exist between the direct determinations 
of the heat of solution of simple substances made by BeRrrueELOT 
and THomsrn, the cause of which it is not easy to conceive }). 
As the mean value of g we will take — 3680 cal. 
5. Introducing the values found into the equation 
and expressing them in electrical units, we find ; 
dE 3680! I 
(|) —_— — Patil = = ~~ 0.51 Milhvoliz: 
d T. 39° 23.09 312 
1) As one of the many examples which might be advanced in support of this, I 
take here the heat of solution of Pb (NO,), which is, according to BerTueLor, 
— 4,1 K., according to Thomsry, — 3.8 k. 
