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Volume Additions, Correction For
When significant amounts of preservative are used, a volume correction
should be made. This will account for the acid added to preserve the
sample and the base used to adjust the pH to the range of the procedure.
This correction is made as follows:
1. Determine the total volume of initial sample, acid added and base
added.
2. Divide the total volume by the initial volume.
3. Multiply the test result by this factor.
An example:
A one-liter sample was taken and preserved with 2 mL of nitric acid. It
was neutralized with 5 mL of sodium hydroxide, 6 N. The result of the
analysis procedure was 10.00 mg/L. What is the volume correction
factor and correct result?
1.
Total volume = 1000 mL + 2 mL + 5 mL = 1007.
2.
3.
10.00 mg/L x 1.007 = 10.07 mg/L = correct result
The addition of a Sodium Carbonate Anhydrous Power Pillow does not
need to be corrected for.
1007
1000
= 1.007 = volume correction factor
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