The calculated free chlorine concentration of the St. Lawrence University pool water was 0.6867 mg/L, which was determined using absorbance spectroscopy. A stock solution of free chlorine solution was used at various volumes, and was diluted by water in a volumetric flask. Then DPD free chlorine powder pillows were added to each, and their absorbance was measured using a visible absorption spectrometer. The concentrations and absorbance of these four solutions were then used to create a graph to formulate the standard curve based upon Beer’s Law. The pool water sample followed the same steps as the previous solutions and absorbance was plugged into the standard curve. The calculated concentration of free chlorine concentration was much lower
