( 340 ) 
The heat evolved by the fusion of one molecule of ZnSO,.7H,0, 
q, 18 
== — 3609 calories. 
Db. Experimental determination of g. 
To determine g, the heat of solution of Zn SO,.7H,O in 393 
mol. H.O0 (final concentration therefore Zn SO,.400 H.O) was first 
determined just below 39°, and then the heat of solution of the 
system which is formed from Zn SO,. 7 H3O above 39° in the same 
quantity of water. The difference between these quantities of heat 
is the value of g required. 
In order to keep the water in the calorimeter at 39° it was sur- 
rounded with a metallic mantle with double walls which in its turn 
was wrapped in felt. Water at about 60° was poured into this mantle. 
The Zn SO,.7H,0 was weighed out in thin walled flasks which 
were then sealed up and kept for some days in a thermostat at 
39°.0. From this they were transferred immediately to the calori- 
meter. When the heat of solution of the system 
(0.941 Zn SO,. 6 HO + 0.162 Zn SO, 12.79 H,O) 
was to be determined the flasks, filled with Zn SO,.7H,O, were 
placed in a thermostat at 42° for 14 days and nights after which 
they were kept in a thermostat at 39°.1 for some days. Asa control 
other flasks were treated in the same way for a shorter time; both 
evolved the same amount of heat when dissolved, a proof that the 
desired condition had been attained. 
a. Determination of the heat of solution of Zn SO4. 7 HO — 
ZnSO4,.400H,0 at 39°. 
Zn SO4,.7 H,0 used = 20.333 gr. 
Water value of calorimeter ete. = 530 er. 
ti == 13.699 
ty — 13.120 At= 0.579. 
f solution = pes < 530 X — 0.579 X 0,970 = — 4219 cal 
Heat of solution EN es 5 579 X 0, Are Özal 
The specifie heat of the final solution was 0 970. 
