Emulsification and demulsification processes are widely used in practice in technological processes of various industries, including oil and chemical industries. With the appearance on the market of multiphase flowmeters for measuring the flow rate of hydrocarbon wells, the question of creating a reference base for research of their metrological characteristics has arisen. In multiphase measurement standards of the Russian Federation, as a rule, a mixture of water, water simulant (Exxsol D100) and atmospheric air is used as a measured medium simulating oil-gas-water mixture (well fluid). The current State primary special standard of mass flow rate unit of gas-liquid mixtures GET 195-2011 is based on the principle of circulation of a liquid mixture of a given composition. However, the long preparation for the transition to a different content of components in the mixture required the development of a new standard, which uses the principle of pre-separation of the liquid mixture with the subsequent separate feeding of components into the mixer of the measuring section. Such principle of multiphase mixture flow reproduction is realized in most foreign multiphase test benches, but at high flow rates there is an acute problem of qualitative separation of liquid mixture depending on the separator capacity. In order to investigate the process of mixing and separation of two liquids, to study the mechanism, flow structure and the time required for their complete separation, experimental setups were created. As a working medium in the experiments was used a liquid mixture consisting of the components used in GET 195-2011. The research results were used in the development of a separation unit as part of the mass flow rate standard for gas-liquid mixtures.