Abstract: A device for the measurement of the amounts of components of loose mixtures comprises a beta radiation source, a backscattering detector, a casing integral with a tribranched hollow chamber, divided at its branching point by a beta radiation-permeable membrane, to form a top branch to contain the sample mixture, and bottom branches leading to the detector inlet and source, respectively, and a lid to close the top branch. The lid is linked to the source to place it in an "on" position on closure. The detector feeds via a comparator, an anticoincidence circuit, whose second input is connected to a tuned generator and whose output feeds a reversible counter via a double frequency divider. Instead a frequency divider may follow the comparator. This may be adjustable with a second frequency divider preceding the second input of the anticoincidence circuit.