Abstract: The modular chemical analysis system includes a first module or sample preparation apparatus for preparing sample solutions, a second module including a nephelometer apparatus comprising a stationary flow cell, mechanisms for moving sample solutions into and out of the flow cell, light generating means for passing light through the flow cell, electric circuitry for sensing the relative light scattered (R.L.S.) by the solution or particles in the solution in the flow cell and a third module comprising a microprocessing/calculator having a tape cartridge program. The microprocessor is coupled to the nephelometer apparatus (and, if desired, is also coupled to the sample preparation apparatus) for controlling operation of the nephelometer apparatus (and, if desired, to control the sample preparation apparatus). Also, the output from the nephelometer apparatus is coupled to the microprocessor which receives R.L.S. values and known concentration values for some solutions from which R.L.S. values were obtained.