Abstract: Apparatus is described which is useful for determining the water content of a petroleum product. The apparatus includes a reaction vial disposed within a tubular member containing a fluid. As the petroleum product reacts with a reactant in the vial a gas is produced in proportion to the amount of water present in the sample. The gas displaces a liquid from the tubular member, and the amount of liquid displaced is proportional to the amount of water which was present in the petroleum sample.

Abstract: 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.