Page 41 - Statistics presented by Dr. Sara Ismail Aborass

9/8/2023

COLORIMETRIC METHODS IN WATER ANALYSIS :

⚫ The color is developed for the sample and standard
(containing known quantities of the pure substance)
solutions

⚫ The color is measured using either a photometer or
Nessler's tubes.

Photometric measurement technique :
Develop the color for the sample and a series of standard.

Measure the absorbance at λmax using a spectrophotometer.
Determine the unknown concentration of sample from the
standard calibration curve.

79

Absorb
-ance

A
sample

Unk. Conc. of sample Conc, ppm

Nesslerization technique :

Using two identical Nessler's tubes, the sample and
standard are treated similarly and the colors
developed are balanced together by changing the
path length in one tube until a matching point is
reached.

80

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