Patent ID: 7372572

Claim:
An apparatus for the photometric measurement of concentration of at least one chemical substance in a solution, comprising: a cuvette, for containing the solution, said cuvette being transmissive for electromagnetic radiation, at least in predetermined regions; a transmitting unit, which produces electromagnetic radiation in at least two wavelength regions and radiates into said cuvette, wherein the electromagnetic radiation in a first wavelength range serves for measuring purposes and wherein the electromagnetic radiation in a second wavelength region is used for reference purposes, and wherein the electromagnetic radiation in the two wavelength regions takes the same path through said cuvette and through the solution; at least one detector unit, which is so arranged that it receives the electromagnetic radiation in the at least two wavelength ranges following its passage through the solution; and a control/evaluation unit, which determines the concentration of the chemical substance in the solution on the basis of the electromagnetic radiation detected in the two wavelength regions, wherein: said control/evaluation unit controls said transmitting unit in a manner such that it alternately emits the electromagnetic radiation in said at least two wavelength regions.