An electrochemical method is used to measure the mean mass transfer coefficient between falling vertical submerged single or multiple circular jets of liquid and a horizontal surface of mercury. The mercury surface is deformed by the jets; its area is increased by a maximum factor of 30%. Correlations of the results are established. The case of single jets is described similarly to the problem of mass transfer in a laminar boundary layer developed over a solid flat plate. For multijets, the correlations are empirical, but theoretical considerations were made for the particular case of turbulents jets.