52 
Proceedings of Royal Society of Edinburgh, [jan. 17 , 
[Na 2 ,0] = 99760 [Na 2 , S, O 4 ] =328590 
[S, O 3 ] =103240 [Na 2 SO 4 , 10H 2 O] = 19220 
203000 
Difference 144810 
347810 347810 
Now, how is this difference of 144810 units accounted for? We 
have first [Na 2 S] = 88200, and then we know that Na 2 0 on being 
dissolved in water evolves 55500 units of heat, which on my 
principles are due to its unexhausted affinity for the O of the water ; 
this affinity acts upon the O of the S0 3 . Thus we have — 
Na 2 S] = 88200 
Na 2 0, O] = 55500 
143700 
We have also heats of neutralisation and solution as follows : — 
[Na 2 0, Aq] = 55500 [Na 2 , O] = 99760 [Na 2 , S, O 4 ] = 328590 
[SO 3 , Aq] =39170 [S, O 3 ] =103240 203000 
N eutralisation = 31378 
125590 
Difference 458 
126048 126048 
Heat of solution = 460 
The balance of 18760 units of heat in the formation of the crystal- 
line salt appears as a negative quantity on solution as in the 
analogous lime salt. 
I have made a few determinations of the quantities of some 
compounds dissolved in water to see how far these conclusions 
derived from thermo-chemistry are borne out by actual quantities 
dissolved. 
In my last paper I stated that the heats of solution of chlorides 
varied directhj as the affinity of the metal for O, and inversely as its 
affinity for Cl. Consider the following table : — 
MC1 2 - MO, Aq. 
Ca = 20560 
Sr = 26770 
Ba = 35980 
Quantity of MC1 3 dissolved in 
100 parts of Water. 
63 grains. 
46 
35 
3 ) 
33 
