1887.] Mr W. Durham on Laws of Solution. 383 
In this diagram there are several points worthy of particular 
notice. 
1. Although given to illustrate solution it would equally well 
illustrate the relations between [M,X 2 ] and [M,0,Aq], which 
are relations of chemical affinity. 
2. The rapid rise of heat of solution after Na and K. I have not 
data for Rb and Cs, but have no doubt they would exhibit 
analogous relations, and have connected them by dotted lines 
to Sr and Ba. 
3. After each rapid rise there are several chlorides which are more 
or less decomposed by solution. These chlorides occur 
between Li and FI, A1 and Cl, Ca and Mn, Zn and Br, Sr 
and Rh, and Sn and I, perfectly regular recurring pheno- 
mena. 
4. The peculiar nature of the curve between Mn and Zn noticed 
in many other phenomena, and especially the sudden rise 
from Cu to Zn, this latter relation is repeated between Ag 
and Cd. Now, it is remarkable that the atomic weights of 
Cu and Zn are almost exactly as much lower than the atomic 
weight of Br as those of Ag and Cd are than that of I, the 
next negative element. 
5. The first maximum point is at Al, whose atomic weight is 
almost exactly midway between the atomic weights of FI and 
Cl. The next maximum is Ni, with atomic weight between 
Cl and Br. The third maximum should be at Rh, but data 
are wanting. 
6. The curve between Hg, Tl, and Pb suggests a repetition of the 
curve between Ni, Cu, and Zn, 
7. The remarkably regular relations between Ca, Sr, and Ba, 
whose chemical similarity is well known. 
If we pass from chlorides to bromides or iodides the change in 
the heat of solution can be represented by a very simple formula. 
For instance, the change from chlorides to bromides is as follows : — - 
Heat of Combination. 
< [M,C1 2 ] ) r M,Br 2 ] 
1 — [H 2 ,Cl 2 Aq]j - t - [H 2 ,Br 2 ,Aq] 
VOL. XIV. 19/1/88 
Heat of Solution. 
= [MBr 2 ,Aq] - [MCl 2 ,Aq] , 
2 b 
