In the work on the extraction of molybdenum from ores carried out by the Scientific Research Department of the Leningrad Mining Institute, the issue of recovering molybdenum from leaching solutions arose. Since electrolytic deposition, due to its greater operational simplicity, yields a product in the form of an oxygen compound of molybdenum that is free from other metals and distinguished by higher purity, it is of great practical interest to study the process of cathodic deposition of molybdenum hydroxide from its solutions. In the experiments described below, we experimentally studied the course of the process of electrolytic deposition of hydroxide from solutions of ammonium molybdate. The influence of various factors, such as the concentration of molybdenum in the solution, current density, temperature, and the concentration of salts of other metals, on the hydroxide deposition process was investigated. The presented results show that for satisfactory cathodic deposition of molybdenum hydroxide, a number of conditions must be observed (see the article).

In this work, the method of direct measurement of the transition resistance, as well as the thickness of the gas film that gives rise to it, was employed using alternating current superimposed on the polarizing direct current. This work allows the following conclusions to be drawn: 1) the existence of transition resistance at a mercury cathode is beyond doubt; however, transition resistance is not the sole cause of hydrogen overvoltage; 2) the formation of a hydrogen film that gives rise to transition resistance begins at very low cathodic polarization; 3) the maximum resistance of the film corresponds to the beginning of the increase in current on the current density-potential curve; 4) with an increase in direct current density, the magnitude of the transition resistance decreases.