Color, True and Apparent
Color, True and Apparent
ColorTru_None_Other_PCS_Eng_Ody.fm Page 3 of 4
Accuracy Check
Standard Solution Method
Prepare a 250 platinum-cobalt units standard as follows:
1. Using Class A glassware, pipet 50.00 mL of a 500 Platinum-Cobalt Units
Standard Solution into a 100-mL volumetric flask. Dilute to the 100 mL mark
with deionized water.
2. To adjust the calibration curve using the reading obtained with the
250 platinum-cobalt units standard, touch
Options on the current program
menu. Touch
Standard Adjust.
3. Touch
On. Touch Adjust to accept the displayed concentration (the value
depends on the selected units). If an alternate concentration is used, touch the
number in the box to enter the actual concentration, then touch
OK. Touch
Adjust.
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
Method Performance
Precision
Standard: 250 units Pt-Co
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Summary of Method
Color may be expressed as “apparent” or “true” color. The apparent color
includes that from dissolved materials plus that from suspended matter. By
filtering or centrifuging out the suspended materials, the true color can be
determined. The procedure describes true color analysis. If apparent color is
desired, it can be determined by measuring an unfiltered water sample. The
stored program is used for both forms of color.
The stored program is calibrated in color units based on the APHA-
recommended standard of 1 color unit being equal to 1 mg/L platinum as
chloroplatinate ion. Test results for Programs 120 and 125 are measured at
455 and 465 nm, respectively.
Program 95% Confidence Limits of Distribution
120 245–255 units Pt-Co
125 245–255 units Pt-Co
Program Portion of Curve ∆Abs ∆Concentration
120 Entire Range 0.010 17 units Pt-Co
125 Entire Range 0.010 17 units Pt-Co
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