Abstract: A spectrographic analysis method which is photometric and non-contact for determining the presence of a chosen constituent in water is provided based on the fact that the inverse of reflectance is a measure of absorption. A full spectrum measurement of the reflectance of the water is made and an absorption spectrum calculated which is then fitted to a clear spectrum in a wavelength range where the water absorption dominates so as to have scaling and offset. Then the clear water spectrum is subtracted and a matching is repeated for the spectrum of the desired constituent and thus a measure of the concentration of the constituent in the water is obtained.

Abstract: A photometric analysis method in which non-absorbed and back scattered light is eliminated in a spectrometer to allow real time analysis of an unconcentrated water suspension without any treatment of the water. Ideally a diffuser is used and the spectrometer (9) is mounted at a slant to obviate fouling of the end glass 2. The spectrometer (9) is a multi-fiber input spectrometer which allows real time calibration of the spectral absorption coefficient.