National Field Manual for the Collection of Water-Quality Data
TWRI Book 9
Calibration is required for the pH instrumentfollow instructions in NFM 6.4.
Alkalinity and ANC determinations require the use of an acid titrant with a known concentration. Accurate standardization of the acid titrant is essential.
|The normality of locally prepared titrant or 0.01639N solution obtained from the OWQRL must be tested once per month. The acid is checked against a fresh standard solution of sodium carbonate, as described below.|
|Record on field notes any correction factors necessary to compensate for cartridge manufacturing anomalies and/or variations in the stated acid normality for the lot of prefilled cartridges to be used. This information is available from OWQRL for USGS personnel.|
CAUTION: When diluting concentrated acids,
Prepare a sulfuric acid titrant solution:
To prepare your own acid titrant for the buret system, follow the procedure below (adapted from Fishman and Friedman, 1989).
This recipe results in an acid concentration of roughly 0.018N. To determine the actual acid concentration, the solution must be standardizedfollow the procedure on the next page. If a concentration of exactly 0.01639N is desired, the standardized solution may be diluted with DIW and restandardized.
Prepare the standard solution:
To prepare a fresh standard solution of 0.01639N sodium carbonate (Na2CO3):
Standardize the sulfuric acid:
Ca is acid normality, in equivalents (eq) per liter, and
Va is volume of sulfuric acid added to reach the equivalence point, in milliliters.