Procedure designed to operate a Coriolis measuring device for measuring a mass flow or a flow velocity of a medium flowing through at least one measuring tube with at least two immiscible components (K1, K2), which comprise a first component and at least a second component, wherein each measuring tube has an inlet (10.1) and an outlet (10. 2), wherein at least two sensors measure vibrations of the measuring tube generated by at least one exciter, wherein the sensors are arranged one after the other in the direction of a measuring tube center line (10.3), wherein a first sensor (11.1) measures, at a first sensor position, at least a first vibration characteristic, on the inlet side, of the measuring tube vibration, and a second sensor (11.2) measures, at a second sensor position, at least a second vibration characteristic, on the outlet side, of the measuring tube vibration, wherein a local concentration variation or frequency variation of the at least one second component influences the measuring tube vibration in an area of the local concentration variation or frequency variation, wherein the influence leads to a variation of an amplitude and/or a phase and/or a vibration frequency of the measuring tube vibration, characterized in that in a first procedural step, a movement of the local concentration variation or the local frequency variation is measured by means of the at least two sensors, wherein a temporal curve of the vibration characteristic measured by the first sensor is compared to a second temporal curve of the vibration characteristic measured by the second sensor, wherein, in the event of a time-shifted occurrence of a variation of the first curve in relation to a variation of the second curve, one concludes the presence of a local concentration variation or a frequency variation of the at least one second component, and in that, in a second procedural step, a speed of the at least one second component is calculated on the basis of the measured movement of the local concentration variation or frequency variation, wherein the speed of the at least one second component is calculated on the basis of the temporal offset of the occurrence of the variations. wherein each measuring tube has an inlet (10.1) and an outlet (10. 2), wherein at least two sensors measure vibrations of the measuring tube generated by at least one exciter, wherein the sensors are arranged one after the other in the direction of a measuring tube center line (10.3), wherein a first sensor (11.1) measures, at a first sensor position, at least a first vibration characteristic, on the inlet side, of the measuring tube vibration, and a second sensor (11.2) measures, at a second sensor position, at least a second vibration characteristic, on the outlet side, of the measuring tube vibration, wherein a local concentration variation or frequency variation of the at least one second component influences the measuring tube vibration in an area of the local concentration variation or frequency variation, wherein the influence leads to a variation of an amplitude and/or a phase and/or a vibration frequency of the measuring tube vibration, characterized in that in a first procedural step, a movement of the local concentration variation or the local frequency variation is measured by means of the at least two sensors, wherein a temporal curve of the vibration characteristic measured by the first sensor is compared to a second temporal curve of the vibration characteristic measured by the second sensor, wherein, in the event of a time-shifted occurrence of a variation of the first curve in relation to a variation of the second curve, one concludes the presence of a local concentration variation or a frequency variation of the at least one second component, and in that, in a second procedural step, a speed of the at least one second component is calculated on the basis of the measured movement of the local concentration variation or frequency variation, wherein the speed of the at least one second component is calculated on the basis of the temporal offset of the occurrence of the variations.