Probe for the simultaneous measurement of scattered light and light absorption at one wavelength or at two different wavelengths, comprising: a) optical elements for guiding and collimating transmission light, scattered light or radiation; b) a first housing having a first through-recess and a second through-recess, the first and second through-recesses connecting a first end of the first housing and a second end of the first housing, the optical elements for guiding and collimating the transmission light or scattered light being comprised in the first and second through-recesses, the first housing further having a first window at one end of the first through-recess and a second window at one end of the second through-recess, for the passage of transmission light, or light, and scattered light, the windows being located at the first end of the first housing; c) a second housing, - the second housing being closed at a first end by a lid, the second housing having a third recess comprising the optical elements for guiding and collimating radiation and having a third window for the passage of radiation at a second end of the second housing, which is arranged opposite the first and second windows, or - the second housing having no recess and having a mirror arranged at a second end of the second housing opposite the first and second windows; d) at least one spacer between the first end of the first housing having the first and second windows and the second end of the second housing having the third window, or the second end of the second housing having the mirror, which has a length of at least 3 mm; e) a closure or a device for closure for connecting the first housing to a container or a tube, by which the interior of the container or the tube is hermetically sealed from the surroundings, the closure being fitted to an outer surface of the first housing said outer surface of the first housing being designed as a screw thread. a) optical elements for guiding and collimating transmission light, scattered light or radiation; b) a first housing having a first through-recess and a second through-recess, the first and second through-recesses connecting a first end of the first housing and a second end of the first housing, the optical elements for guiding and collimating the transmission light or scattered light being comprised in the first and second through-recesses, the first housing further having a first window at one end of the first through-recess and a second window at one end of the second through-recess, for the passage of transmission light, or light, and scattered light, the windows being located at the first end of the first housing; c) a second housing, - the second housing being closed at a first end by a lid, the second housing having a third recess comprising the optical elements for guiding and collimating radiation and having a third window for the passage of radiation at a second end of the second housing, which is arranged opposite the first and second windows, or - the second housing having no recess and having a mirror arranged at a second end of the second housing opposite the first and second windows; - the second housing being closed at a first end by a lid, the second housing having a third recess comprising the optical elements for guiding and collimating radiation and having a third window for the passage of radiation at a second end of the second housing, which is arranged opposite the first and second windows, or - the second housing having no recess and having a mirror arranged at a second end of the second housing opposite the first and second windows; d) at least one spacer between the first end of the first housing having the first and second windows and the second end of the second housing having the third window, or the second end of the second housing having the mirror, which has a length of at least 3 mm; e) a closure or a device for closure for connecting the first housing to a container or a tube, by which the interior of the container or the tube is hermetically sealed from the surroundings, the closure being fitted to an outer surface of the first housing said outer surface of the first housing being designed as a screw thread.