Ivanovich: I. I. Borgman, N. A. Gezehus, N. G. Egorov, K. D. Kraevich, F. F. Petrushevsky, etc. While studying the “spiritualistic phenomena”, the methods of natural sciences, instruments and calculations were broadly used. The conclusions of the commission were joined in the book, published by D. I. Mendeleyev, “The materials for commenting the spiritualism.” The funds, made by selling this book, were meant for “making a big balloon and in general for the research of the meteorological phenomena of the top layers of atmosphere.”
The versatility of personality and variety of interests of Mendeleyev are striking. But the scientist himself used to say so: “I respect one-sided talents, but, nevertheless, I consider them to be a certain abnormality. I like science most of all, but I think that I could have specialized in other spheres under the certain circumstances. I think that a normal person can orient everywhere.”
Mendeleyev was depressed by the end of the 1870’s. The state of his health had become worse. He had been taken ill with pleurisy and he had to go abroad for the treatment. Besides, his relationship with his wife Theozva Nikitichna was cooling down more and more.
In spring of 1877 his wife with the children goes to Boblovo. And the sister of Dmitry Ivanovich Katya comes temporarily with the children to his apartment. Anyuta Popova, the daughter of a Don Cossack, lived as a guest with Nadezhda, the niece of Mendeleyev. She studied at the Conservatoire in the class of piano; she visited the painting school attached to the Academy of Arts. Infatuation of Dmitry Ivanovich for her grew into love. However, Anyuta was more than 20 years younger than Mendeleyev. They were called Faust and Margaret behind their back.
Dmitry Ivanovich suffered deeply while struggling with his feeling. He considered necessary to tell everything to father of Anna Ivanovna, and the last one asked him not to meet with Anyuta anymore. The girl went abroad, but Mendeleyev followed her to Rome. In 1881, after having returned, he wrote to Theozva Nikitichna: “Yesterday I came back to Petersburg with Anna Ivanovna and her father Ivan Eustacievich…
My position is clear and specified already by this. If nothing extraordinary happens, it will stay being like that, and I will stay at the University, I will start lecturing and working as usual, and, in addition, I will solicit to have funds for 2 families.” “We’ve lived, we will stay being friends though not in one house.”
Theozva Nikitichna hasn’t agreed for the divorce for a long time. The marriage was dissolved only in 1881. In winter of the same year Lyuba, the daughter of Anna Ivanovna and Dmitry Ivanovich, was born. They could get married only in 1882. After the wedding the Mendeleyevs settled in the university apartment. Here their younger children were born later: a son Ivan and twins, Maria and Vasiliy, who were called in honour of the mother of Dmitry Ivanovich and his uncle Vasiliy Kornilyev, who had done many things for the Mendeleyevs in his time.
This period was a hard one for D. I. Mendeleyev also by another reason. It seemed to him that he didn’t have enough energy in order to realize his creative potential sufficiently. However, he kept working, and the periodical law, discovered by him, got more and more followers among the scientists of the world.
From the very beginning appeared the question of the priority of the discovery, started by the number of English and German scientists: W. Odling, L. Meyer, etc., in connection with the fundamental importance of the law. Mendeleyev devoted his publication “To the question of the system of elements”, which appeared in the “Reports of German Chemical Society” in 1871, right to this problem. In his small article the scientist mentioned the most important stages of his discovery and suggested for the first time to call his system periodical, because of the periodical law being its basis: “The measurable chemical and physical characteristics of the elements and their connections depend periodically on the atomic weights of the elements.”
The article “The periodical legality of the chemical elements”, which was the result of more than two years of work of the scientist, was published in 1871 in the “Annals of Pharmacy” (“Annalen der Pharmacie”), the oldest chemical magazine, founded in 1832 by the German chemist J. Libich. That is the evaluation of this article by Mendeleyev at the end of the 1890’s:
“This is the best code of my opinions and considerations about the periodicity of elements and this is the original, according to which there was written so much about this system. This is the main reason of my scientific reputation…”
In the same article the scientist gave the criterion of the solidity of the laws of nature in general: “Every law of nature gets the scientific meaning only in case that it, so to say, allows practical consequences, i. e. such logical conclusions, which explain unaccounted and point to the phenomena unknown before, and especially if the law leads to the predictions, which may be checked by experiment. In the last case the meaning of the law is evident and it is possible to check its equity, which at least impulses to the development of the new spheres of the science.”
By applying this thesis to the periodical law, he mentioned the following opportunities of its application: 1) to the system of elements;
2) to the definition of the characteristics of yet unknown elements;
3) to the definition of the atomic weight of scantily explored elements;
4) to the correction of the values of atomic weights; 5) to the renewal of the data concerning the forms of chemical compounds. Besides, Mendeleyev pointed to the possibility of “application of the periodical law: for the correct idea of the so-called associated compounds; for the comparative research of the physical characteristics of simple and compound bodies.” Mendeleyev thought when the physical sense of the periodical law would have been understood and the essence of the elements’ distinction would have been discovered on this basis, “then, certainly, chemistry would be able to leave the hypothetical field of static ideas, which are dominating there nowadays, and then there would be an opportunity to place it under the dynamic direction, which is already applied productively enough to the study of most of the physical phenomena.”
It is possible to say that the scientist outlined by this article the broad programm of the research on the subject of inorganic chemistry, based on the law of periodicity. Indeed, many important directions of inorganic chemistry were developed actually at the end of the 19th – beginning of the 20th century according to the ways, designed by D. I. Mendeleyev.
In March of 1879 there was an important event, which promoted the further consolidation of the periodical law in the science: the Swedish chemist L. Nilson told about having discovered scandium, which appeared to be the same with ekabor of Mendeleyev. However, L. Nilson defined the chemical nature of scandium incorrectly first, holding that the new element should have been placed for certain between tin and thorium in the periodical system. The identity of scandium and ekabor was clearly determined in August of 1879 by the countryman of Nilson P. Kleve. And in 1880 L. Nilson admitted the rightfulness of P. Kleve.
Thus, if the discovery of gallium by P. Lecock de Boibodrant in 1875 only confirmed the opportunities of the periodical system, the discovery of scandium made the chemists look at it as at a strict scientific generalization of data and facts, as to the guide to the further research of chemical elements. In 1884–1887 the periodical law became consolidated and was acknowledged by the vast majority of those scientists, who hadn’t made a proper account of it or ignored it at all.
In 1884 the “problem of beryllium” was finally solved. Up to that moment there hadn’t been any united standpoint concerning the valency of this element and the value of its atomic weight. On April, 17th (5th) L. Nilson wrote a letter to Mendeleyev, where he was stating all the data concerning beryllium and was warmly congratulating him with the fact, “that also in this case, as in many others, the system justified itself.” The discovery of the new chemical element germanium in the rare mineral argyrodite, made by K. Winkler in 1886, became an especially important event of that
