The DPD colorimetric method is used to determine the amount of residual chlorine in the sample. In this method, the free chlorine in the sample oxidizes the colorless amine N,N- diethyl-p-phenylenediamine to a colored compound that absorbs strongly at 520 nm. The analysis of a set of calibration standards gave the following results: ppm Cl2 Absorbance 0.00 0.0031 0.50 0.1232 1.00 0.3241 1.50 0.5438 2.00 0.7642 2.50 0.9551 3.00 1.1565 A 10.00 mL water sample from a public water supply was diluted to 250 mL and analyzed for free chlorine residual, giving an absorbance of 0.3210. A. Find the equation of the line. B. What is the molar absorptivity of Cl2 (FW = 70.9) at 250 nm? C. Calculate the free chlorine residual of the sample as ppm Cl2.
The DPD colorimetric method is used to determine the amount of residual chlorine in the
sample. In this method, the free chlorine in the sample oxidizes the colorless
diethyl-p-phenylenediamine to a colored compound that absorbs strongly at 520 nm. The
analysis of a set of calibration standards gave the following results:
ppm Cl2 Absorbance
0.00 0.0031
0.50 0.1232
1.00 0.3241
1.50 0.5438
2.00 0.7642
2.50 0.9551
3.00 1.1565
A 10.00 mL water sample from a public water supply was diluted to 250 mL and analyzed
for free chlorine residual, giving an absorbance of 0.3210.
A. Find the equation of the line.
B. What is the molar absorptivity of Cl2 (FW = 70.9) at 250 nm?
C. Calculate the free chlorine residual of the sample as ppm Cl2.
D. Calculate ppm BaCl2 (FW = 208.2)?
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