( 338 ) 
Between — 5° and the transition point the solubility of Zn SO. 
7H, O is well represented by the equation: 
Ly = 41.80 + 0.522 t + 0.00496 2 
whilst the equation which I have deduced from the determinations 
of CALLENDAR and Barnes between 39°.9 and 50°.2, viz.: 
Ly = 59.34 + 0.0054 ¢ + 0.00695 t° 
holds good, according to my determinations, to 25°. The figures, 
marked in the table with asterisks are calculated from this 
expression. 
From the above interpolation formulae the following table (LD), 
which will be used subsequently, is obtained. 
In it A is the number of molecules of water to one molecule 
of Zn SO, in the saturated solution of the system ZnSO, . 7 H.0, 
whilst « is the same quantity for the system Zn SO, . 6 H,0. 
ADE Be 
Temperature A a 
39°.0 12.79 12.79 
35°,0 13.54 13.13 
30°.0 14.47 13.65 
25°.0 15.46 14.16 
15°.0 17.65 15.67 
Se | 19.08 16.53 
0°.1 21.43 18.11 
: di . es ‘ 
4. The calculation of = (equation 2) and also of £ requires a 
F 
knowledge of the value of g. 
At the transition temperature, g is the heat of fusion of Zn 504. 
7 H,O. This quantity may be determined in two ways, 
a. By extrapolation from THOMSEN’s figures. 
b. Experimentally. 
