540 Proceedings of the Royal Society 
already operated upon; to enter more minutely into the various 
phenomena ; and to determine the law of what I may call 
“ Solution Equivalents.” To know, for instance, the relation 
between the quantity of calcium chloride dissolved and the 
quantity of common salt precipitated or hydrochloric acid gas 
expelled from solution, and various other points which suggest 
themselves for investigation. 
The experiments, however, so far as they go, seem to point to 
certain conclusions which are interesting and suggestive. 
1st. There seems to he a regular gradation of chemical attraction 
from that exhibited in the suspension of clay in water up to that 
exhibited in the attraction of sulphuric acid for water which we call 
chemical affinity. The attraction of clay for water is not so strong 
as the attraction of salts which are dissolved in water. Then again, 
the attraction of salts is not so strong as that of hydrochloric acid, 
which almost forms a definite chemical compound with water. 
Then, finally, we reach sulphuric acid with the strongest attraction of 
all, and forming more than one definite chemical compound with 
water, and easily displacing from their combinations with water 
hydrochloric acid ; salts it does not decompose and clay in sus- 
pension. 
2d. That chemical combination , solution , and suspension diffie 
only in degree , and are manifestations of the same force. The few 
drops of sulphuric acid added to the water with clay in suspension 
attracts and holds the water with the same force as a salt in solution 
and precipitates the clay in the same manner, and as the water 
is evaporated increases its hold gradually on what remains until it is 
strong enough to form definite chemical compounds. 
3d. The attraction of chemical affinity is not , in all cases at any 
rate , exhausted when a definite compound, is formed , but has sufficient 
power left to form solution or suspension compounds. Thus calcium 
sulphate is a definite chemical compound, but it still possesses 
sufficient affinity for sulphuric acid to enter into solution with it. 
This view would explain the researches of M. Stus on atomic 
weighs He proved that Prout’s law, that the atomic weights of the 
elements are simple multiples of that of hydrogen, is not correct, 
though very nearly so ; the differences being very small fractional. 
If it be true that the attraction of affinity is not entirely exhausted 
