Hach Chemical Company

Paul E Larson

David J Schoonover

A method for compensating for error in amount of indicator added to a sample under test in bleaching chemistry analysis involves adding a reagent system comprising an indicator and a dye in relative amounts such that the indicator at one wavelength (the 'measuring' wavelength) and the dye at a different wavelength (the 'reference' wavelength) exhibit the same absorbance at zero concentration of the parameter of interest. Error in the amount of indicator added to the sample is compensated for by measuring the decrease in absorbance at the measuring wavelength after reaction of the indicator with the parameter of interest, against the absorbance at the reference wavelength.

Method for spectrophotometric compensation for colorimetric reagent

An improved nephelometer comprised of a transparent cell for containing a liquid sample, a light source, and a detector is disclosed which reduces the amount of stray light reaching the detector. The cell is characterized in that either the illuminating light beam or the detected light passes through the cell wall face at an acute angle to the normal to the cell wall face.

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Fort Collins, CO, United States of America

Paul E Larson