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POPULAR SCIENCE REVIEW. 
of the union of oxygen and silver, i.e., of oxygen with an electro- 
positive element, belongs to the class of basic oxides. 
If this view of the composition of oxides were granted — and 
a most ingenious and plausible theory it was — why should we 
not proceed a step further and say that an acid acts so readily 
upon a base, because in the first, negative electricity predomi- 
nates, while the prevailing electricity in the latter compound is 
positive ? 
And in further support of this view could it not be 
experimentally demonstrated that when a salt, such as sulphate 
of sodium, is decomposed by the electric current, the soda goes 
to the negative pole, whilst the sulphuric acid appears at the 
positive pole ? The experiment of decomposing a solution of 
sulphate of sodium was frequently performed, and the fact, 
that if the solution were coloured with litmus, that portion 
around the negative pole retained its blue colour, whilst that 
around the positive pole became red, was regarded as con- 
clusive evidence of the dualistic structure of the salt operated 
upon. 
But about the year 1834 Dumas told the chemical world 
that chlorine was capable of ‘ laying hold of the hydrogen of 
certain bodies and replacing it atom for atom/ If this be so, 
said Berzelius, the compound formed must differ essentially 
from that from which it is derived. Chlorine is an electro- 
negative element, and if it enter into a compound in place of 
the electro-positive hydrogen, the original compound and the 
new compound can present no points of analogy. The theory 
seemed correct, but unfortunately the chlorinated body did 
present very marked analogies with that from which it had 
been produced. Berzelius attempted many explanations, in- 
vented many new compound groups of atoms, which should 
be supposed to enter into the composition of the new bodies 
discovered by Dumas ; but his electro-chemical theory was 
doomed. It was gradually abandoned^by most chemists, and 
the substitutionists carried the day. 
Berzelius had largely availed himself of certain facts, which 
showed that, in series of reactions, it was sometimes possible for 
a group of dissimilar atoms to remain intact, to move about, so 
to speak, from one compound to another without falling to 
pieces. Reasoning on these facts, he constructed formulae for 
all compounds, which formulae were made up of two parts, or 
radicles. The idea of compound radicles was thus closely 
associated with the dualistic theories of the Berzelian school* 
The new school, led by Dumas, finding dualism insufficient to 
explain many weighty facts, naturally waged war against the 
fundamental conception of compound radicles, but they were 
soon obliged to accept the essential truth of the theory which 
