Mendeleev and the Rare-Earth Crisis - Philosophy of Chemistry - page 166

substructure.” 51 Bernadette Bensaude-Vincent as well, claimed that the elements
“could never be divided” according to Mendeleev s opinion. 52 Finally, the Japanese

historian, Masanori Kaji asserted that “Mendeleev regarded atomic theory with
caution” and Kaji therefore thought it reasonable “to suppose that [Mendeleev]
refined the concept of the elements to bear an attribute of an individual chemical
entity without employing the notion of atoms because of the supposed limitations of
the atomic theory.” 53
How to explain this difference in opinion? As we have argued elsewhere, 54
Mendeleev did believe in atoms in 1869. But these viewpoints no longer surfaced in
the papers which were written at a later stage of development of the periodic law
(i.e. during the post-1869 period). At that time, Mendeleev had indeed radically
changed his viewpoints concerning the existence of atoms. He thus emphasised in
1871 that “one cannot harmonise the periodic law and the atomic theory without
upsetting the known facts.” 55 Since the expression atomic weight implied “the
hypothesis of the atomic structure of matter”, Dmitrii Ivanovich proposed to replace
this expression with “elementary weight” as it seemed to him that this would
“avoid the concept of atoms when speaking of elements.” 56 Such statements from
the post-1869 period have led the majority of historians to the wrong conclusion
that Mendeleev never believed in atoms. It appears that Nathan Brooks has been
one of the few historians thus far in emphasising Mendeleev

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s speculations on the
complexity of the elements in 1869. He thus clearly stated that “Mendeleev did not
reject the complexity of elements in the first few years after his discovery of the
periodic law.” 57
Thus ended the first period of Mendeleev

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s research which lasted from 1869 till
the end of the first half of 1870. Mendeleev

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s viewpoints could be summarised
as follows. According to his opinion, chemists had to draw a sharp distinction
between primary (i.e. rare earths, transition metals) and secondary elements
(i.e. alkali metals, halogens). Such a differentiation should also be made on the

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51 Gordin, M. D. A Well - Ordered Thing : Dmitrii Mendeleev and the Shadow of the Periodic Table .
New York: Basic Books, A Member of the Perseus Books Group, 2004. (pages 24-25) Emphasis
in original.
52 Bensaude-Vincent, B., op. cit. p. 7. (note 40)
53 Kaji, M. “D. I. Mendeleev ' s Concept of Chemical Elements and the Principles of Chemistry.”
Bulletin for the History of Chemistry 27, no. 1 (2002): 4-16. (page 6-7) Emphasis added.
54

Thyssen, P. “Mendeleev ' s Periodic Table and the 19th Century Debates on Atomism.” In Wald ,
Positivism and Chemistry . Edited by M. Eisvogel and K. Ruthenberg. W¨rzburg: Konigshausen
and Neumann, 2014 (in press).
55

Mendeleev, D. I. “Die Periodischen Gesetzm¨ssigkeit Der Chemischen Elemente.” Annalen der
Chemie und Pharmacie 8 (Suppl.) (1871c): 133-229. English translation in Mendeleev, D. I. “On
the Periodic Regularity of the Chemical Elements.” (1871c/t) In Mendeleev on the Periodic Law ,
Selected Writings , 1869 - 1905 , ed. William B. Jensen, 38-109. Mineola, New York: Dover
Publications, Inc., 2002. (page 58)
56 Ibid., p. 40 & 106.
57 Brooks (2002), op. cit., p. 142. (note 10)