Please feel free to request a detailed description. Short description: Mendeleev, D.I. [Isomorphism in connection with other relations of crystalline shape to composition. Dissertation presented at the end of the course at the Main Pedagogical Institute by student D. Mendeleev]. Izomorfizm v svyazi s drugimi otnosheniyami kristallicheskoj formy k sostavu. Dissertaciya, predstavlennaya pri okonchanii kursa v Gl. ped. in-te studentom D. Mendeleevym. - Saint Petersburg: printing house of I.I. Glazunov and Co., 1856. In Russian. Dmitri Ivanovich Mendeleev's dissertation, Isomorphism in connection with other relations of crystalline shape to composition, defended in 1856, was his first significant scientific work and was dedicated to studying the correlation between the chemical composition of substances and their crystalline structure. Mendeleev built upon the work of the German chemist E. Mitscherlich, who introduced the concept of isomorphism a phenomenon in which different substances have similar crystalline forms. In his work, Mendeleev proved that the shape of crystals is determined not only by their composition but also by the chemical structure of compounds. He also studied the influence of impurities on the crystal lattice and concluded that even minor changes in composition affect the physical properties of substances. An important contribution of this study was the identification of analogies between elements and their compounds, which served as one of the prerequisites for the development of the Periodic Law of Elements. SKUMS002350