In his autobiographical notes written in his old age the scientist referred to the doctors error good-humouredly.  But when he had heard this verdict in his youth, he was quite aggrieved.  Nevertheless, he collected all his will and continued his studies. 

He had a great zest for life.  To him life meant the opportunity to learn and work. 

Mendeleyev is best known for his work on the Periodic Law, which he discovered at the age of 35. Once he was asked what had led him to that discovery. He answered he had suspected connections between elements for a long time, and worked much to record such connections in the form of a table. Just before formulating the Law he was overwhelmed by a deep despair and fell asleep in his study. In his sleep he saw the table of chemical elements he had sought to formulate for such a long time.  Even in his sleep his joy was so great, that he awoke and scribbled it hastily on the first piece of paper he could lay his hands on.

His discovery of the Periodic Law made Mendeleyev famous overnight, but conceit was foreign to him. The scientist used his prestige only once, for a very weighty reason. It was the time of student riots during which a prominent botanist Academy member Famitsin, was arrested. After three behind bars he was ordered to appear before General Gurko. Mendeleyev decided to accompany him. The  general  began  to shout  at  the  two  professors.   The botanist was confused. But Mendeleyev' s reaction was different. He also began to shout. “How dare you threaten us? Who are you? A martinet, nothing else. In your ignorance you do not even know who I am. The name of Mendeleyev went down in history. Do you know that he made a revolution in chemistry, that he discovered the periodic system of elements? Answer me, what the periodic system is!” The general was evidently unaware of that system and this embarrassed him. The meeting ended in a triumph of science. Mendeleyev and his friend withdrew in dignity, and the chemist said: “Now he will not dare to suppress the university.”

Mendeleyev was not only a brilliant scientist, but also an excellent teacher. His lectures were extremely popular.  Mendeleyev infected his listeners with the desire to study.   This was one of his major goals. “We must develop our natural resources scientifically - iron  in  the  Urals  and  in  Siberia, cements from  our  own  minerals, paints  from  our  own  oil, glass  from  our  own Glauber's salts. Our resources are limitless, and we must train our own scientists, whose strong point is realism. Russia must  take  care to  produce  its  own  Platos  and  Newtons.”

Unfortunately, Mendeleyev had to leave the university because he had supported his students’ petition, which clearly was of a political character. It was a courageous deed.   However, it was not in his nature to hold grudges, since he worked in science for the benefit of Russia, not himself. Mendeleyev wrote more than 500 works in different areas of knowledge for the sake of his nation. His inquisitive mind worked to develop agriculture, glass production butter making, spiritism, aeronautics, philosophy, and each of his works reflected shrewdness and common sense.

Mendeleyev died on January 20th, 1907, with a pen in his hand, his writing ending in the following words: “I find it necessary to express in general terms…”