The mixing process in the near wake of a circular cylinder was studied by measuring instantaneous values of the local concentration. A conductivity probe (space resolution 6.5 x 10(-5) cm(3)) was used for the measurement of the instantaneous concentration in a system composed of two liquid streams (water and NaCl in water solution) originally separated by a splitter plate. The flow in the test section was confined by the side walls of the channel. The purpose of the work was to study wake scalar transport at high Schmidt numbers. In the present case the Schmidt number was around 700. Data were acquired at cylinder Reynolds numbers in the range of 200-650. A global picture of the mixing process was obtained independently from a visual study; the experiment involved photographing the process of a diffusion controlled chemical reaction (a pH indicator, phenolphthalein, in one stream and NaOH-solution in the other). Various statistical quantities of the concentration signals, characteristic for the mixing process were computed. An interpretation of the data is presented from the point of view of instantaneously occurring flow structures in the wake of the cylinder.