Chemistry Reference
In-Depth Information
Mendeleev. After his discovery of the periodic system in February 1869,
Mendeleev tirelessly laboured at the clarification, illustration, refinement, and
optimisation of his periodic classification of the elements. Not surprisingly, the
accommodation of the rare-earth elements formed an important part of Mendeleev
s
research program, which lasted approximately 2 years—from 1869 till 1871. But at
the end of 1871, Mendeleev threw in the towel, distancing himself from the various
discussions concerning the placement of the rare earths which were held at the end
of the nineteenth century.
Notwithstanding the fact that Mendeleev failed to resolve the rare-earth crisis, he
definitely grasped the essence of the subject-matter better than any other chemist at
the time. More importantly, the rare-earth elements also played a key role in
inducing a number of important changes in Mendeleev
'
s deep, almost philosoph-
ical, viewpoints with regard to the
epistemological concept of a chemical element
and the
nature of elementary groups
. The unexplainable properties and mystifying
character of most rare earths made him question the current definition of a chemical
element, as well as the validity and universality of the periodic law, and even led
Mendeleev into hypothesising about the internal structure of matter and constitution
of atoms.
The aim of this research paper is twofold: First of all, the early history of the
accommodation of the rare-earth elements in the period 1869-1871 will be retraced.
Secondly, and most importantly, the principal content of this paper intends to clarify
some of Mendeleev
'
s perceptions about primary and secondary groups, the elements
as basic and simple substances, and the use of short and long form tables.
Since Mendeleev
'
s viewpoints underwent some crucial changes around the
second half of 1870, our historical argumentation will be built around two sections.
The first section (Sect.
11.1
) centres on the period from Mendeleev
'
s discovery in
February 1869 till the end of the first half of 1870. The second period which
extended from the second half of 1870 to the end of 1871 will be dealt with in
the second section (Sect.
11.2
). A summary of our principal conclusions can be
found in Sect.
11.3
.
'
11.1 The Period 1869-1870
11.1.1 A Septuplet of Homeless Elements
Nearly 150 years ago, on the 17th of February 1869,
4
a pamphlet was printed with
the aim of circulating it among the most distinguished Russian and European
4
All events in Russia are dated according to the Julian calendar (Old Style), which was used in
Russia until January 1918. It lagged 12 days behind the Gregorian calendar (New Style) in the
nineteenth century, and 13 days in the twentieth. For example, February 17, 1869 (Old Style)
corresponds to March 1, 1869 (New Style), as can be seen on Fig.
11.2
. Gregorian dates will be
given for all events occurring outside Russia.
