770 
MR. BRODIE ON THE CONDITION OF CERTAIN ELEMENTS 
the whole of the peroxide of barium is deeomposed, prussian blue is produced in 
abundance. In this experiment one atom of oxygen is first added, and this atom 
is then removed by the contact of another atom under suitable circumstances. I infer 
therefore from these experiments, not that the oxidation is a necessary antecedent to 
the disoxidation, but that the spontaneous decomposition of the oxidized body and 
the reduction of the chromic acid, where no oxidation takes place, and the oxidation 
of the body, are due to one and the same cause, namely, to the mutual attraction of 
the elemental particles. When, for example, arsenioiis acid is oxidized by the action 
of chlorine, I consider that the oxygen is oxidized as well as the arsenic. We are 
led to the same conclusions by various well-known experiments ; in the case, for ex- 
ample, of the decomposition of the nitrate of ammonia on boiling, when this com- 
pound breaks up into water and nitrogen, thus — 
NO 4 H4N=4HO-fN2; 
) 
while from no point of view is it very logical to draw a distinction between two facts 
so very similar as the formation of the water and the nitrogen, it is proved, by the 
experiments 1 have cited, that the mutual attraction of the particles of the nitrogen 
is a most important condition of the change. 
The transition from these cases of spontaneous decomposition to other instances, in 
which no one of the substances usually called compound is formed, but the elements 
alone are liberated, is obvious ; and I cannot but think that these phenomena, viewed 
as the last of a series of chemical changes, proceeding from the simplest case of 
double decomposition to the curious experiments I have just cited, each successive 
link of which is bound to the preceding by the closest analogies, reasonably admit of 
a very different interpretation to that which we should put upon them when regarded 
out of this connection. It is hard to draw a distinction between the decomposition 
of the chloride of nitrogen and of the nitrite of ammonia. From quite independent 
considerations, the conclusion is forced upon us, that the mutual attraction of the 
particles of chlorine and of nitrogen plays a most important part in other cases of 
chemical change. Why may we not admit that in this case the decomposition is de- 
termined solely by these relations ? The heat which attends upon this and other 
similar decompositions is, on the electro-chemical theory, as confessed by its greatest 
supporters, an inexplicable enigma. Fleat is the constant sign of combination, but 
here it asserts is only decomposition, so that theory and fact are plainly at issue. On 
the other hand, admitting that in this experiment the formation of the elements is a 
true chemical synthesis, the evolution of heat is accounted for ; and as the elements, 
chlorine and nitrogen, are far more permanent forms of matter, and less readily altered 
by chemical action than the chloride of nitrogen, so it is reasonable to believe that the 
particles of which they are composed are in a far more intimate state of combination. 
The transition from these experiments to the most ordinary cases of the formation of 
