300. Affinity and Fleat, 
Yet an exclusive value must not be given to these 
differences, in the chemical properties to designate a com-. 
bination in the physical properties to designate a solution. 
We all know from the beautiful experiments of Henry Rose, 
that very weak solutions of the alkaline carbonates of borax 
have reactions differing essentially from those which their 
concentrated solution present. This remark is sufficient 
once more to show that the phenomena due to changes 
of state, cannot be ranged in two distinct categories, com- 
bination and solution. I shall recur to this once more, in 
reference to diffusion, or the indefinite extension of matter 
in menstrua. 
What I have said, enables me to use the two words 
—combination and solution—in a perfectly definite sense, 
without the risk of considering them to express an un- 
known cause, and characterizing them simply by the 
effects which are manifested in our daily chemical opera- — 
tions. I hope, therefore, to be logical, in the following 
-reasonings :— 
When two gases are mixed, which spread uniformly into - 
one another, can the phenomena of what is called their - 
diffusion be compared to the solution of two liquids in one - 
another? I donot think so. _ ) 
Suppose we place together bisulphide of carbon and 
white phosphorus, at a temperature convenient for the 
melting of the phosphorus, oil and sulphuric ether, 
chloride of calcium dissolved, acetic acid and water. We | 
might obtain very decided changes of physical condition, » 
characterized principally by an elevation or depression of 
temperature, and by a change of density: in a word, the 
physical properties of these solutions might vary without 
the chemical propeities being sensibly modified. 
Is this the same with gases? Experiment shows us, 
first of all, that gases frequently combine without apparent 
absorption, or disengagement of heat (oxide of carbon and . 
chlorine, chlorine and hydrogen in diffused light). But 
whenever this disengagement of heat can be confirmed, 
the chemical properties have been profoundly changed. 
Moreover, Gay Lussac’s law proves that gases which con- 
tract in combining, do not change in volume in the same - 
way as liquids which dissolve. The volume of the com- 
bination is always a simple fraction, and. often a very small ~ 
one, of the volume of the elements of this combination, 
Thus, contraction, when it exists, not merely characterizes . 
the combination of the eases, but always the composition 
to be deduced therefrom. ¢ 
