Abstract: A process cell (1) for the analysis of liquids, particularly cloudy ones with high light absorption, has a measuring chamber (2) through which flows said liquid, which has two windows (3) lying at a short distance opposite each other for the passage of the measuring light. The latter are held in holding devices (4) which are supported by a common frame (5), which is sufficiently movable relative to the cell housing (6) to be able to perform heat movements. The frame (5) and the holding devices (4) consist of a material with essentially the same coefficient of thermal expansion, so that changes in length of the holding devices (4) occurring upon temperature changes can each time be compensated so that the distance between the two windows (3) practically does not change and thus no changes in the measuring results determined by temperature fluctuations occur.