Mendeleevs Rare-Earth Research

It can be mentioned here that another pioneer of the periodic system, the German Julius Lothar Meyer (1830-1895) did not list the rare earths in his first periodic table, because he was not convinced that the rare earths were genuine elements (van Spronsen, 1969). He also foimd that their atomic weights had not been determined with sufficient accuracy. 

he accepted the elemental nature of the rare earths and he tried to place them in the periodic table according to a homologous accommodation methodology, as Mendeleev did. In 1876, Meyer placed cerium, erbium, and yttrium in the boron group as trivalent elements, but he placed lanthanum in the column of the tetravalent elements. 

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The Czech chemist Bohuslav Brauner (1855-1935) (Figure 8) read Mendeleev s 1871 paper about six years later (Brauner, 1930 Druce, 1944). It made such an impression on him that he decided to refocus his experimental research on finding a solution for the question of the position of the rare earths in the periodic system. Brauner became the main defender of the periodic system in late nineteenth century. His rare-earth research has been of great importance in the further resolution of the so-called "rare-earth crisis," i.e., the problematic accommodation of the rare earths in the periodic system. It was especially Mendeleev s change of the atomic weights that had drawn Brauner s attention. It appears that although Brauner doubted the homogeneity (read elementarity) of... 

It should be mentioned here that there had been a close contact between Mendeleev and Braimer via correspondence (Brauner, 1930 Kedrov and Chentsova, 1955). The correspondence between Brauner and Mendeleev is of great historical interest. Its content clearly demonstrates how these two chemists mutually influenced each other during the period 1881-1907, and it provides us with new insights into Brauner s rare-earth research. Luckily, Mendeleev was a very orderly man, who carefully maintained even the most minor notes and letters which he received from others, especially when the content of these letters was related to his scientific activities. Mendeleev brought all these letters... 

Mechanical milling, 292, 295 Mechanochemical method, 419 Medical applications, 146 Medium-long forms of the periodic table, 81 Melting point of rare-earth metals, 80 MEM. See Maximum entropy method Mendeleev, Dmitrii Ivanovich, 8,37 line, 15 method, 24 methodology, 37 active rare-earth research, 25... 

Mendeleev said, more than elsewhere in the system of elements, that new invesligatiOTis are to be desired and for which the periodic law provides guidance. About 6 years later, the yoimg Czechoslovakian chemist, Bohuslav Brauner, discovered Mendeleev s wonderful communication . It made such a profound impressimi 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 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. ... 

Bohuslav Brauner had approached the rare-earth crisis from a fradifional chemical poinf of view. Bofh the search for higher valencies and complicated atomic weight determinations had been central to his research during the last quarter of fhe nineteenfh century, but neither of fhese methodologies allowed to prove the validity of the homologous accommodation. Brauner s adherence to the Mendeleev method had led him to a... 

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. 

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. 

The dual sense of the epistemological concept of chemical elements has been the focus of much philosophical debate and research by contemporary philosophers of chemistry. Although this debate goes back to the 1931 paper by Paneth, the main idea was clearly already present in the Mendeleev corpus." It is therefore interesting to investigate to what extent the rare-earth crisis forced Mendeleev to change his points of view with regard to the nature and concept of elements. 

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

The reason why Mendeleev asked for some specimens of rutile, ilmenite and zirconium should be clear by now. But why was he in need of orthite, cerite, and eschynite Both cerite and eschynite are rich in cerium (and to a lesser degree also in lanthanum and yttrium). The mineral orthite, on the other hand, is not only abundant in cerium, it also contains substantial amounts of the other rare-earth elements. Obviously, Mendeleev was not only planning to discover the unknown eka-sihcon, he also hoped to perform some experimental research on the rare earths in order to resolve their problematic accommodation. 

Thus ended Mendeleev s experimental research on the periodic law as well as his rare-earth investigations. In July 1871, Mendeleev composed his German landmark article on the periodic law, which was translated into German by Felix Wreden and which appeared in Liebig s Annalen in November 1871—symbohsing Mendeleev s last research paper on the periodic law. °... 

At the end of December 1871, Mendeleev abruptly started a new research project on gas expansion. Even though there still remained some problems with the periodic law, such as finding the predicted elements and determining the places of the rare earth elements, Mendeleev did not seem to have sufficient patience to continue the experimental work that these problems necessitated. Instead, he directed his attention to the expansion of gases, explaining that this new research was a search for a true physical foundation of the periodic law. ... 

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