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SILVER, continued
SAMPLING AND STORAGE
Collect samples in acid-cleaned plastic or glass bottles. Using pH paper,
adjust the pH to 2 or less with nitric acid (about 2 mL/liter). Store
preserved samples at room temperature for up to six months. Adjust the
pH to 9 to 10 with 5.0 N sodium hydroxide before analysis. Correct for
volume additions; see Sampling and Storage, Volume Additions,
(Section 1) for more information.
ACCURACY CHECK
Standard Additions Method
a) Add 5.0 mL of 1000-mg/L Silver Standard Solution to a 100-mL
volumetric flask. Dilute to volume with demineralized water. Mix well.
This is a 50-mg/L silver standard solution.
b) Use a TenSette Pipet to add 0.1, 0.2 and 0.3 mL of this standard
solution to three 50-mL samples (or sample portions diluted to 50 mL).
Mix well.
c) Analyze as described above. Each 0.1 mL addition of standard should
increase the silver concentration by 0.1 mg/L.
d) If these increase do not occur, see Standard Additions (Section I) for
more information.
Standard Solution Method
Prepare a 0.50 mg/L silver standard solution as follows:
a) Use a TenSette Pipet or 1.0-mL volumetric pipet to add 1.00 mL of
Silver Standard Solution, 1000-mg/L Ag, into a 100-mL volumetric
flask to prepare a 10 mg/L Ag working solution.
b) Dilute to the mark with demineralized water. This solution should be
prepared weekly.
c) Pipet 5.00 mL of the working standard into a 100 mL volumetric
flask. Dilute to the mark with demineralized water. This 0.5 mg/L Ag
solution should be prepared daily.
d) Perform the silver test as described above.
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