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In-Depth Information
Mendeleev said, “more than elsewhere in the system of elements, that new
investigations are to be desired and for which the periodic law provides guidance.”
81
About 6 years later, the young Czechoslovakian chemist, Bohuslav Brauner,
discovered Mendeleev
s “wonderful communication”. It made such a profound
impression on him that he fixed his life
'
s aim at that very moment: “it was the
experimental research of the solution of the following problems: What is the
position of the so called rare elements and especially those of the rare earths in
Mendeleev
'
s system?”
82
Brauner would become the main defender of the periodic
system in the late nineteenth century, and his rare-earth research became of the
utmost importance for the further resolution of the rare-earth crisis. But that is
another story.
83
'
11.3 Conclusions
Dmitrii Ivanovich Mendeleev definitely grasped the essence of the rare-earth crisis
better than anyone else. His train of thought had been meticulously written down
in a number of papers on the periodic law during the period 1869-1871.
But Mendeleev not only circumscribed the rare-earth problem, he also significantly
aided in partly resolving the crisis. Thus Mendeleev corrected the atomic weight
values of the rare-earth elements by increasing their valency from 2 to 3, and he
attempted to accommodate these metals on an individual basis according to a
homologous placement. From the very beginning in 1869, Mendeleev had a
sound conception of the difference between primary and secondary groups of
elements. He discerned basic substances from simple substances, and he knew the
advantages and disadvantages of both the short and long form tables.
Since Mendeleev
s viewpoints underwent some crucial changes around the
second half of 1870, this paper was divided in two main parts. The first period
was characterised by Mendeleev
'
s use of a
long form
periodic table (the
Attempted
System
, Figs.
11.1
and
11.2
) and his attempt to accommodate the rare-earth
elements as a
group
. The rare earths thus constituted a primary group of primary
elements, undermining both the periodic law and the characterisation of basic
substances by their atomic weights. The old, Berzelian atomic weights were used
throughout and Dmitrii Ivanovich endeavoured to grasp the rare-earth crisis by
drawing an analogy between these elements and the so-called transition metals.
'
81
Mendeleev (1871c/t), op. cit., p. 81. (note 55)
82
Brauner, B. “D. I. Mendeleev as Reflected in His Friendship to Professor Bohuslav Brauner.”
Collection of Czechoslovak Chemical Communications
2 (1930): 219-243 (page 231).
83
Thyssen, P., and K. Binnemans. “Accommodation of the Rare Earths in the Periodic Table: A
Historical Analysis.” In
Handbook on the Physics and Chemistry of Rare Earths
, edited by K. A.
Gschneidner, 41, 1-94. Burlington: Academic Press, 2010.
