many prominent scientists of Europe. Those were J.– B. Dumas, Ch. Wurza and S. Cannizzaro, G. Rosko, etc. He continued communicating with them later.
It is difficult to overestimate the meaning of the International chemical congress in the history of chemistry. There was accepted the common system of atomic weights and were defined the conceptions of the molecule and atom.
As stated above, the scientific conceptions, which had been generally acknowledged at the congress of 1860, appeared in Mendeleyev’s research even before; the fundamentals of the molecular theory, as well as the principles of defining the molecular weight and density, were delivered by him at his lectures.
At the beginning of the 1860’s another important event took place in the life of D. I. Mendeleyev. On April, 29th of 1862 there was a wedding of Dmitry Mendeleyev and Theozva Nikitichna Leshchova, the stepdaughter of Pyotr Petrovich Ershov, the authour of the fairy-tale “Konyok-Gorbunok” (“The gibbous horse”). The wife was six years older than her husband. Their first-born son was Volodya, then daughter Olga was born. But this marriage wasn’t a happy one. Active work of a scientist, his uneasy way of life appeared to be far from the supposed ideal of wife. Interests and characters of this married couple were too different. At the beginning of the 1870’s their relationships started being complicated. Theozva Nikitichna gave her husband absolute freedom under the condition that the official marriage wouldn’t have been annulled.
In spite of the difficult relationships with his wife, D. I. Mendeleyev always behaved towards the family very carefully and responsibly. Especially he loved children, he often said, “Whatever I do and, however, I’m busy, I’m always happy when any of them comes to me.” The only thing, which could interrupt his work, were the children. If he suddenly heard the children’s screaming or crying, right away he rushed to find out what had happened. He used to come running and frightened, screamed loudly and threateningly, but in no circumstances at the child, but at the nunny. The nunny experienced it almost always and the children – never. Dmitry Ivanovich said, “I experienced many things in my life, but I don’t know the better happiness than to see my children next to me.”
His niece Nadezhda Yakovlevna Kapustina-Gubkina remembered that he loved and worried not only about his own children. In Boblovo – the estate purchased by D. I. Mendeleyev in 1865 on an equal footing with his friend N. P. Ilyin – in summer there were having rest several families with their children. The kids were always around the master of the house, they used to walk with him on his household business. It was interesting for them to listen to the stories of Dmitry Ivanovich, to walk with him about the forest, to share with him their joys and sorrows.
N. Y. Kapustina-Gubkina remembered an episode, which had vividly illustrated Dmitry Ivanovich’s delicacy towards the child’s soul, his kindness, “In the morning my elder brother and sister were teaching us in Russian and in French. I perplexed in my translation and my sister was keeping me for a long time under the lesson. Dmitry Ivanovich was passing by the sitting-room, where we were studying, and told my sister casually:
– Why are you exhausting her over the book, Anyuta? Let her walk, she will have time.
Right away I ran away, but after forty years I remember how kind he was towards the child’s soul.”
D. I. Mendeleyev is a scientist, a teacher, a public figure
The 1860’s became for Dmitry Ivanovich Mendeleyev the time of realization of the significant research of scientific and applied nature. Here the amazing correlation of theoretical works of the scientist and their practical application became apparent.
Later his son Ivan Dmitrievich Mendeleyev wrote about his father, “I knew as though two Mendeleyevs. One of them was an assiduous collector of facts, a petty empiricist – Wagner of Goethe, for whom the highest pleasure was the treatment of the number, piling of the data, examination of interesting individual features of the phenomena. Another one was the valorous Faust, passing away to the “spirits’ world”, to the world of ideas, to the world of general laws…”
In 1861, at the suggestion of the “Public Good” Publishing House, D. I. Mendeleyev wrote a manual of organic chemistry, which became the first Russian textbook on this subject. The basis of this manual was the series of lectures delivered by him in 1857–1858. The book was written during the extremely short term and it caused the broad response in the scientific and public groups. Mendeleyev was awarded to a prize of the Academy of Sciences, and in 1863 the second edition of the manual was published.
Mendeleyev also started to edit the Technical Encyclopedia in many volumes “Technologies according to Wagner” (Wagner J.– R. Theorie und Praxis der Gewerbe: Hand und Lehrhuch der Technologie). Wagner’s Encyclopedia was published in Leipzig in 1857–1860 and had a great success in Europe. First, D. I. Mendeleyev decided to make a translation only because of the lack of money. He remembered, “I started translating and completing the “Technologies according to Wagner” because it was paid (30 rubles per sheet), but then I was interested and made many additions…”
The work on editing this book took several years. Dmitry Ivanovich not just translated the “Technologies…” from German, but he made a large amount of adjustments, sometimes completing the book with his own chapters. After all, the “Technologies according to Wagner” played a significant role in the choice of the future subject of the scientist’s research. In the third part of the “Technologies…” there were discussed the scientific and technological problems, connected with alcohol production. The practical importance of precise data about the density of alcohol-aqueous solutions and theoretical meaning of these data combined in this question. Density had been always considered by D. I. Mendeleyev as the most important parameter of substance. By the middle of the 1860’s the scientist started paying less attention to the edition of the “Technologies according to Wagner” and was more and more concentrated on the research of the alcohol-aqueous solutions.
In 1863, in connection with the development of the technology of alcohol-aqueous industry, Mendeleyev started a new big series of science works on this subject. On the first stage he was constructing the instruments for defining alcohol concentration – alcoholometers. And on the next stage – the thorough research of relative density of alcohol-aqueous solutions in the whole interval of concentrations under several temperatures. This experimental work became the foundation of the Doctoral thesis, which was presented by him to the Council of Petersburg University at the end of 1864 and was defended by him in 1865.
The research “About the connection of alcohol with water” contains the basic regulations of Mendeleyev’s doctrine of the solutions and it especially determines the existence of water and alcohol connections. Here are the results of measuring the density of aqueous solutions of ethyl alcohol with 35 to 100 % of alcohol according to weight under five values of temperature (0°, 10°, 15°, 20° and 30 °C).
It is necessary to thank Dmitry Ivanovich Mendeleyev that Russia was possible to give the world its famous Russian vodka. V. Pohlebkin in his article, devoted to the Mendeleyev’s research, wrote, “D. I. Mendeleyev, who had taken part in his time in the creation of the contemporary scientific technology of vodka production, insisted definitely on making the general official name “vodka” as the most exactly expressing the character of the drink.
Till the establishment of the vodka monopoly in 1894–1902, vodka had been produced very easily – by mixing up 50 % of alcohol with 50 % of water. Such a mixture gave 41–42° of alcohol in the drink. In order to get the forty-degree vodka, it was necessary not to combine volumes but to weigh alcohol precisely. Mendeleyev proved that 40°, which is indeed never got by mixing up the volumes of the water and alcohol, but only by mixing up the precise weight ratio of alcohol and water, should have been acknowledged as the ideal content of alcohol in vodka.
Thus, one litre of forty-degree vodka should weigh
