Abstract: A method of on-line controlling and optimizing industrial chemical processes for the manufacture of textile finishing and improving agents to achieve an optimum end point, wherein the improvement comprises the steps of periodic automatic sample taking, over at least the critical state of the process, injecting the samples into a carrier stream, optionally physically and/or chemically manipulating the samples while in the carrier stream, and then transporting the carrier stream to a detector wherein one or more values are measured, said values being used to adjust the process to an optimum end point. The method not only makes possible to determine and monitor the instantaneous state of the process but also, because of the amount of relevant data per unit of time resulting from the method, to drive the process to a desired quality by using the data obtained from the detector for further process control. Each new analysis affords a prognosis on the further reaction course and on the end point of reaction.