The invention relates to an infrared measuring device, especially for the spectrometry of aqueous systems. Said device comprises at least one measuring unit, especially a measuring cell, also comprising at least one ATR-body and at least one infrared light source. The measuring unit contains at least one ATR-body which comprises at least two planar, substantially parallel limiting surfaces and which is transparent with respect to measuring radiation and which has an index of refraction which is greater than that of the medium which is arranged next to at least one limiting surface and which is to be examined, especially larger or equal to 1.5. The IR-measuring radiation on at least one of the planar, parallel limiting surfaces of the ATR-body can be totally reflected in an attenuated manner by at least six times.