FIELD: measurement technology.SUBSTANCE: method and apparatus for recognizing the liquid, which contains positively charged particles and/or negatively charged particles, are provided. According to the invention, the electric field is applied to the liquid by means of applying voltage to the positive electrode and to the negative electrode, which is located in the liquid, in order to attract the negatively charged particles to the positive electrode in order to concentrate the negatively charged particles in the first part of the liquid, and to attract the positively charged particles to the negative electrode in order to concentrate the positively charged particles in the second part of the liquid, where the voltage is controlled based on at least one of the weight of the charged particles and the weight of the charged particles. First recognition result is obtained by means of recognizing at least one part of the liquid from the first liquid part, the second part of liquid and the third part of liquid, in w
