Julius Lothar Meyer (1830 1895) was active in many fields of chemistry. He designed much new apparatus, determined physical constants, and studied problems of organic chemistry. Meyer had been strongly influenced by the ideas of Cannizzaro and first presented his ideas on the relation of the properties of elements and their atomic weights in 1864. Although he recognized this relationship clearly, he at first devoted most of his attention to the regular differences between the atomic weights of related elements. His ideas underwent further development, however, and by 1868 he had prepared a table which in many respects resembled the present periodic table. He did not publish this work until after the appearance of Mendeleev's first paper on the subject in 1869. His table was very similar to that of Mendeleev, but it contained some improvements and was, perhaps, influential in causing some of the revisions made by Mendeleev in the second version of his table, published in 1870. In general, Meyer was more impressed by the periodicity of the physical properties of the elements, while Mendeleev saw more clearly the chemical consequences of the periodic law. The following selection is taken from the paper in Annalen der Chemie, Supplementband, 7, 354-64 (1870), in which Meyer first fully expressed his ideas.
THE NATURE OF THE CHEMICAL ELEMENTS AS A FUNCTION
OF THEIR ATOMIC WEIGHTS.
The regularities which exist between the numerical values of the atomic weights are not only sought by different authors between very different elements but are also presented very differently. Since we no longer base our consideration of these on the so-called "equivalents" of Gmelin but use the atomic weights determined by the rules of Avogadro and of Dulong and Petit, the presentation of these regularities has been considerably simplified. Even in 1864, I found regularities which brought into one and the same scheme families of chemical elements which until then had been considered different. By the correct determination of different atomic weights, it has since become possible to arrange in the same scheme the elements discovered up to now which are well enough known. Recently
Mendeleev has shown that such an arrangement is obtained if the atomic weights of all the elements, without any arbitrary selection, are simply arranged in a single series according to the size of their numerical values; this series is divided into sections, and these are added together in unaltered succession. The following table is essentially identical with that given by Mendeleev.
Co = Ni = 58.6
Periodic table according to Lothar Meyer,1870
The table contains all the elements whose atomic weights have been determined up to now either by the gas densities of their compounds or by their heat capacities, arranged according to increasing atomic weight, with the single exception of hydrogen, which appears to be anomalous, and including also Be and In, whose probable atomic weights are derived from their equivalent weights; in all, 56 elements. Besides H, it lacks only Y, Eb, (Tb?), Ce, La, Di, Th, U, Jg (Jargonium),1 none of whose atomic weights are known, and even some of whose equivalent weights are unknown. Probably these elements later will, at least in part, fill the blanks which are still found in the table. Other blanks will perhaps be filled by elements to be discovered later; possibly also through future discoveries one or another element will be removed from its place and replaced by a more suitable one.
While the elements follow through the nine vertical rows from first to last according to the size of their molecular weights, the horizontal rows contain the natural families. To obtain this arrangement, some few of the elements whose atomic weights have been found to be nearly equal and which have probably not been very carefully determined must be rearranged somewhat, tellurium before iodine, osmium before iridium and platinum, and these before gold. Whether this reversal of the series corresponds to the properly determined atomic weights must be shown by later researches. Here I will add only one observation to those which Mendeleev made in his table, that the elements standing in vertical rows IV, VI, and VIII are often isomorphically related to those of the next preceding horizontal row; thus, Ti and Zr with Si, V with P, Cr and Mo with S, Mn with Cl, Ag with Na, Zn with Mg, etc. As to the question of atoms, which so far have not been broken down, the table makes plain an especially important conclusion. If we assume that the atoms are aggregates of one and the same material and differ only in their different masses, then we can consider the properties of the elements as depending on the size of their atomic weights; they appear as direct functions of the atomic weight. The table gives us the conception that the properties of the elements are in great part periodic functions of the atomic weight. The same or similar properties reappear if the atomic weight has a certain size, then after 16 units, then about 46, and finally 88 to 92 units. This is true in all cases, whatever the element from which we may start. As striking and attractive as this observation is, however, it leaves us completely in the dark as to the change in properties within the periods at whose ends the properties which were present at the beginning repeat themselves. If, for example, we start from Li, we find that after an increase of nearly 16 units, essentially these properties are found in Na, and again after 16 units, in K. On the way there, however, we encounter in a most varied series first the elements Be, B, C, N, O, F, and then again, Mg, Al, Si, P, S, Cl, apparently without any means of transition; only the saturation capacity of the atoms rises and falls regularly and equally in both intervals.
But if we wish to describe the nature of the elements as depending on the atomic weight, then we must follow step-wise the change of each property from element to element. To obtain a starting point for this is the purpose of the following considerations.
One of the properties which changes quite regularly with the atomic weight is the atomic volume of the elements which is periodic function of their atomic weight.
1Jargonium was claimed as a new element by HC Sorby in Chemical News, 20, 7 (1869), a claim retracted ibid 21, 73 (1870). The spectrum he had seen was due to impure zirconium.
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