acid. But oxygen and sulphur are both electro-negative elements. Berzelius supposed that sulphur contained a large quantity of both electricities, the negative predominating. When this element combined with oxygen, the positive electricity of the sulphur was Supposed to be neutralized by the negative electricity of the oxygen, so that the negative electricity of the sulphur was concentrated or rendered more apparent. The affinity between oxygen and silver is less than that between sulphur and oxygen, because, said Berzelius, silver contains mainly positive electricity, but a smaller quantity than is found in sulphur. The product of the union of oxygen and sulphur, i. e., of oxygen with an electro-negative body, belongs to the class of acid oxides; the product 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 predominates, 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, while 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 colored with litmus, that portion around the negative pole retained its blue color, while that around the positive pole became red, was regarded as conclusive 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, invented 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
