Page:Popular Science Monthly Volume 59.djvu/168

158 groups." "The difference between the number of the lowest member of a group and that immediately above it is seven; in other words, the eighth element starting from a given one, is a kind of repetition of the first, like the eighth note of an octave in music." While this regularity appeared in the case of the elements of low atomic weight, it failed when applied to many of those elements which have a higher weight, and also in the case of iron, cobalt and nickel. These three metals seem to break in upon the octaves, and must be left out of account before the law of octaves can be used. This irregularity Newlands noticed, enunciating his law in the words: "The numbers of analogous elements, when not consecutive, differ by seven, or by some multiple of seven." By 'number' he means merely the number of the element when all are arranged in a series in the order of their atomic weight. There was thus here, as in the work of De Chancourtois, the vision of a certain periodicity in the actual arrangement of the elements, and the recognition of the fact that in some way there is a connection between the properties of an element and its atomic weight. But there seemed to be no suspicion that all the properties of an element are a function, much less that they are a periodic function of its atomic weight.

It may seem strange to us that the work of these two pioneers should have been received with almost complete indifference by chemists. This results in part, at least, as has been pointed out by Mendeléeff, from the too-limited application of Newlands's law. Relations were brought out between little groups of elements, like Döbereiner's triads, but comparisons were not made between dissimilar elements, and even the groups made up by taking the seventh elements often contained those which were far from being similar in their properties. Thus we find the first, and hence analogous, elements of his eight octaves as follows: Hydrogen, fluorin, chlorin, cobalt-nickel, bromin, palladium, tellurium, platinum-iridium. Such a grouping as this could hardly be expected to appeal strongly to chemists, especially as iodin, an element which obviously belongs with fluorin, chlorin and bromin, is relegated to the seventh group of elements. The lack of enthusiasm on the part of chemists at the reception of Newlands's work may be judged from an incident. When his paper was read at the meeting of the Chemical Society, one of the members present asked of Professor Newlands whether he had ever tried arranging the elements according to the order of their initial letters.

The Periodic Law in its present form was first enunciated by Professor Dmitri Mendelèeff, in 1869, in a paper read before the Russian Physico-Chemical Society. It is true that five years earlier Lothair Meyer had published in the first edition of his 'Modern Theory of Chemistry' a list of the elements arranged according to atomic weights.