V. G. Khlopin began his independent scientific activity as a student in 1911 - in his father's laboratory at the Clinical Institute he carried out work, the results of which were published in the article "On the formation of oxidants in the air under the action of ultraviolet rays".

At the initial stage of his research activity (1911-1917), V. G. Khlopin was mainly concerned with problems related to inorganic and analytical chemistry.

Of his further works, especially important are those aimed at the development of a new method for the preparation of various derivatives of univalent nickel, and the creation of a device for determining the solubility of compounds at different temperatures.

Khlopin performed his first technological work - he developed a method of obtaining pure platinum from Russian raw materials.

In the mentioned speech V. I. Vernadsky notes the specific features of the new direction of scientific research: "This discovery has produced a huge revolution in the scientific outlook, caused the creation of a new science, different from physics and chemistry - the doctrine of radioactivity, put before life and technology practical tasks of a completely new kind...".

Khlopin became his life's work, he develops research of scientific and applied aspects, including methods of geochemistry of radioactive elements and noble gases, analytical chemistry and thermodynamics; at the same time, the scientist develops an independent direction, which gave the preconditions for the formation of a scientific school.

A large batch of radium-containing ore from the Tyuya-Muyun deposit was stored in the warehouse of a private commercial firm "Fergana Society for Rare Metals Mining".

This organization, due to the lack of specialists-radiochemists in Russia, was preparing the raw material for shipment to Germany for technological extraction of the final product from it, but the war and then the February Revolution of 1917 prevented this.

Karpov, entrusted the Academy of Sciences with the mission of organizing a plant for radium extraction from domestic uranium-vanadium ores and ensuring scientific control over production; at a meeting of specialists convened on 12 April by the Commission for the Study of the Natural Productive Forces of Russia (NPFR), headed by N. S. Kovalev.

С. Kurnakov, V. G. Khlopin and L. I. Bogoyavlensky it was reported on the results of the work undertaken to obtain radium from the available raw materials; in July 1918 a special Commission, the Technical Council or later the Board for the organization of a radium plant at the Academy of Sciences was elected, which decided to organize a research laboratory, a special Radium Department (under the Commission) headed by V. I. Vernadsky was established under the chairmanship of A. E. Fersman, senior mineralogist of the Academy of Sciences, professor of the Higher Women's Courses.

His thorough theoretical training and mastery of the methods of fine chemical analysis, his ability to solve practical problems effectively, and his experience in expeditions fully justified his involvement in such a responsible business.

[19][22] V. G. Khlopin developed a method of mechanical enrichment to improve the quality of raw barium-radium sulfates rich in silica (together with engineer S. P. Alexandrov).

The possibility of using the method of isomorphic co-crystallization not only for the isolation of radioactive elements, but also for the study of their state in liquid and solid phases - for determining their valence was shown.

In this case, they are similar to anomalous mixed crystals (as shown experimentally by V. G. Khlopin and M. A. Tolstaya), and relate to the latter approximately as a colloidal solution with suspension.

Goldschmidt), up to microscopic - anomalous mixed crystals such as FeCl2 — NH4Cl, Ba(NO3)2, Pb(NO2)2, methylene blue K2SO4 - Ponsorot, etc., showing heterogeneity).

Khlopin proposed the method of isomorphous co-crystallization from solutions for fixation of weightless and unstable chemical compounds and determination of their composition.

The method made it possible to discover and determine the composition of individual compounds of divalent and hexavalent polonium (V. G. Khlopin and A. G. Samartseva).

In this field, the following directions were developed in V. G. Khlopin's works: 1. radioelements migration, in particular - relatively short-lived in the Earth's crust; 2. study of radium-mesothorium containing waters; 3.

The scientist was the first to draw attention to the special importance of studying the migration of relatively short-lived radioelements in the Earth's crust for solving general geological and geochemical problems (1926).

Extensive studies relating to the establishment of the presence of radium, uranium, and decay products of the thorium series in natural brines of the Soviet Union were carried out under the direction of V. G. Khlopin; numerous expeditions revealed a new form of accumulation in nature of radium and its isotopes in brine waters of the Na, Ca, and Cl types.

The scientist supervised research in this direction in the Radium Institute - on helium and lead methods, which gave the determination of the geologic age of some formations.

The work (with E. K. Gerling and E. M. Ioffe) on helium migration from minerals and rocks and the influence of the gas phase on this process should be attributed to this cycle.

In 1924, he and A. I. Lakashuk discovered helium in the gases of the Novouzensky district of Saratov province; and in the period from 1924 to 1936, V. G. Khlopin and his students (E. K. Gerling, G. M. Ermolina, B.

A. Nikitin, I. E. Starik, P. I. Tolmachev, and others) analyzed many samples of natural gases and created a distribution map based on the data.

In accordance with these ideas in underground gas atmospheres there is a gradual enrichment of argon, krypton and xenon, - depletion of neon in relation to their content in the air.

The beginning of this direction of geochemistry was the work on boron-acid springs in northwestern Persia and Transcaucasia; later these studies were extended to other areas of the USSR.

Khlopin also for the first time noted the need for prospecting boron-acid compounds in the Embinsky and Gurievsky counties of the Ural region, where much later the Inderskoye field was discovered.

The neutron-proton theory of the structure of the atomic nucleus owes its origin to the discovery of new elementary particles that make up the nucleus: the neutron (10n) and the proton (11p), which became possible by the artificial splitting of the atom under the influence of α-particles (1919): 147N+42He→178O+11H, accompanied by the release of a proton (soon experiments were carried out with a number of other light elements).

From 1917 to 1924, V. G. Khlopin served as an assistant in the department of general chemistry at the university, and from 1924, as an assistant professor, he began teaching a special course on radioactivity and the chemistry of radioelements - the first in the USSR; since brief and incomplete data and summaries existed only in foreign literature, this course was completely developed by V. G. Khlopin, who taught it until 1930, and resumed in 1934 as a professor, teaching it until 1935.

A. Nikitin and A. P. Ratner, a course of lectures on radiochemistry formed the basis of an extensive monograph on the chemistry of radioactive substances.