The formulation of this definition of chemistry was due to Robert Boyle.
The benzene nucleus presents a remarkable case, which must be considered in the formulation of any complete theory of valency.
An alternative view, due to Green, is that the oxygen atom of the xanthone ring is tetravalent, a supposition which permits the formulation of these substances as ortho-quinonoids.
It cannot be maintained that the ideas of Ephesians directly contradict either in formulation or in tendency the thought of the earlier epistles.
The earliest formulation of the subject, due to Lord Kelvin, assumed that this relation was true in all cases, and, calculated in this way, the electromotive force of Daniell's cell, which happens to possess a very small temperature coefficient, was found to agree with observation.