1887 .] 
Mr W. Durham on Chemical Affinity. 
49 
and we have almost exactly the heat of formation and solution of 
H 2 S0 4 . Thus— 
[H 2 0] = 68360 [H 2 , S, O 4 ] =192920 
[S, O 3 ] =103240 [H 2 S0 4 ,Aq] = 17850 
[S, H 2 ] = 4740 
[SO 3 , 0]= 34413 
210753 210770 
Now, of course, I have assumed that S will develop 34413 units in 
addition after combining with three atoms of O. Let us see, how- 
ever, how this way of looking at the combination helps us as we go 
on. Take next a very different sulphate, viz., BaS0 4 . In building 
this salt up from its elements, 338070 units of heat are evolved. 
Analysing this in the same manner as in the case of H 2 S0 4 we have 
[Ba, O] = 124240 units of heat, [S, 0 3 ] = 103240 units, together 
equal to 227480 units, leaving 110590 units to he evolved on com- 
bination of BaO with S0 3 . Whence do these 110590 units come? 
We have the answer at once when we know that [Ba, S] = about 
109600. It is evident the S acts upon the Ba with as much 
energy as if BaS were actually formed, and this is the cause of the 
combination. In accordance with my theory, the S cannot act to 
any extent on the O of the BaO owing to the energy with which 
the Ba holds the O, being represented by 124240 units instead of 
68360 as in the case of H 2 0. Thus we have — 
[Ba, O] 124240 [Ba, S, O 4 ] 338070 
[S, O 3 ] 103240 
227480 
Difference 110590 = [Ba, S] 109600 
338070 338070 
Further, consider how the heat of neutralisation is accounted for. 
BaO, on being dissolved in water, evolves 34520 units of heat, S0 3 
evolves 39153, and the difference between the sum of these and 
110590 is the heat of neutralisation. Thus — 
[BaO, Aq] = 34520 
[SO 3 , Aq] =39153 
Neutralisation = 36896 
VOL. XIV. 23 / 8/87 
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