Publisher's Synopsis
In measuring a dissolved substance, a concentration of a specific dissolved substance in a sample water is measured using a measuring water W1 developing a specific color within a specific pH range by adding each of two reagents to a sample water W0, and an acid-base indicator S developing different colors other than the specific color is selected in a first pH range including the specific pH range and a second pH range deviating from the first pH range. Next, a reagent is prepared by adding the acid-base indicator to one reagent wherein a pH value of a reagent added water where the two kinds of reagents are separately added to the sample water is within the second pH range. Next, absorbance values are calculated by three region component lights which are a transmitted light in the measuring water wherein the prepared reagent is added.
