A nuclear-magnetic-resonance measurement cell in a liquid medium, comprising: - a reservoir for said liquid medium; - a fluidic circuit connected to said reservoir and comprising a measurement chamber; - a gas injector opening into said fluidic circuit, at a distance from said measurement chamber; and - a coil encircling said measurement chamber; in the measurement cell, the fluidic circuit also comprises a gas outlet port, spaced apart from said gas injector and having a shape such that the introduction of gas by said injector causes the liquid medium to flow through the fluidic circuit; characterised in that: - it also comprises at least one capacitive element forming, with said coil, an electromagnetic resonator; in that: - it has a shape allowing its introduction into a nuclear-magnetic-resonance probe as a replacement for an assembly formed by a standard nuclear-magnetic-resonance tube and a rotor bearing said tube, the coil encircling the measurement chamber then being positioned so as to couple by induction to at least one radiofrequency coil of said probe; and in that - the coil is placed in a portion of the cell intended to occupy, inside the probe, a location provided for the nuclear-magnetic-resonance tube, whereas the reservoir and the gas injector are placed in another portion of the cell intended to occupy, inside the probe, a location provided for the rotor. - a reservoir for said liquid medium; - a fluidic circuit connected to said reservoir and comprising a measurement chamber; - a gas injector opening into said fluidic circuit, at a distance from said measurement chamber; and - a coil encircling said measurement chamber; in the measurement cell, the fluidic circuit also comprises a gas outlet port, spaced apart from said gas injector and having a shape such that the introduction of gas by said injector causes the liquid medium to flow through the fluidic circuit; characterised in that: - it also comprises at least one capacitive element forming, with said coil, an electromagnetic resonator; - it also comprises at least one capacitive element forming, with said coil, an electromagnetic resonator; in that: - it has a shape allowing its introduction into a nuclear-magnetic-resonance probe as a replacement for an assembly formed by a standard nuclear-magnetic-resonance tube and a rotor bearing said tube, the coil encircling the measurement chamber then being positioned so as to couple by induction to at least one radiofrequency coil of said probe; - it has a shape allowing its introduction into a nuclear-magnetic-resonance probe as a replacement for an assembly formed by a standard nuclear-magnetic-resonance tube and a rotor bearing said tube, the coil encircling the measurement chamber then being positioned so as to couple by induction to at least one radiofrequency coil of said probe; and in that - the coil is placed in a portion of the cell intended to occupy, inside the probe, a location provided for the nuclear-magnetic-resonance tube, whereas the reservoir and the gas injector are placed in another portion of the cell intended to occupy, inside the probe, a location provided for the rotor. - the coil is placed in a portion of the cell intended to occupy, inside the probe, a location provided for the nuclear-magnetic-resonance tube, whereas the reservoir and the gas injector are placed in another portion of the cell intended to occupy, inside the probe, a location provided for the rotor.