Morphological studies of Benzene derivatives.—III. Paradibromobenzenesulphonates (Isomorphous) of the “Rare Earth” elements—a means of determining the directions of valency in tervalent elements

In a communication on the “Classification of the Elements” brought under the notice of the Society by one of us in 1902, a method of ordering the elements was advocated which was different, in essential respects, from that we owe to Mendeléeff, more especially in that it involved the systematic application of a principle dominant in organic chemistry—the principle of homology—in a manner and to an extent not generally recognised as necessary at that time. The subject has been further discussed in a recent lecture to the Royal Philosophical Society of Glasgow, various issues being considered which have been brought into prominence in the meantime—e. g . the atomic weights of argon and the allied inert elements, the nature of the radioactive, elements and the position of tellurium in the scheme of elements. An amended table of the elements put forward in the lecture referred to is reproduced on p. 205.