Volatile Acids
Volatile Acids
Page 4 of 6
VolatileAci_None_Other_ESR_Eng_Ody.fm
Standard Solution Method
Prepare a 500 mg/L volatile acid standard solution as follows:
1. Pipet 4.00 mL of a 62,500-mg/L Volatile Acid Standard Solution into a
500-mL Class A volumetric flask. Dilute to volume with deionized water.
Prepare this solution daily. Perform the esterification procedure as
described above.
2. To adjust the calibration curve using the reading obtained with the
500-mg/L standard solution, touch
Options on the current program menu.
Touch
Standard Adjust.
3. Touch
On. Touch OK to accept the displayed concentration. If an alternate
concentration is used, touch the number in the
Adjust to field and enter the
actual concentration. Touch
OK. Touch Adjust.
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
Method Performance
Precision
Standard 625 mg/L as acetic acid (HOAC)
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
The volatile acid test is designed specifically for determining volatile acids in
digestor sludges. The method is based on esterification of the carboxylic acids
present in the sample and subsequent determination of the esters by the ferric
hydroxamate reaction. All volatile acids present are reported as their equivalent
mg/L as acetic acid. Test results are measured at 495 nm.
Program 95% Confidence Limits of Distribution
770 602–648 mg/L HOAC
Portion of Curve ∆Abs ∆Concentration
625 mg/L 0.010 27 mg/L as HOAC
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