- Potassium chromate indicator solution - Dissolve 5 g K2CrO4 in 100 mL deionized water.
- Standard silver nitrate titrant, 0.030 N - Dissolve 5.0964 g AgNO3 in deionized water and carefully dilute to 1 L. To check normality of this solution, titrate against a standard sodium chloride solution. Store silver nitrate solution in a brown bottle. (You don't need to check normality if you weigh out the AgNO3 accurately.)
- Standard sodium chloride, 0.015 N - Dissolve 0.4384 g NaCl (dried at 140oC) in deionized water and dilute to 500 mL.
- 25 mL refilling buret and stand.
- 500 mL volumetric flask.
- 150 mL beaker.
- Magnetic stirrer.
- Pour 50 mL of the sample into a 150 mL beaker.
- If sulfide, sulfite, or thiosulfate is present, add 1 mL H2O2 (30%) to the sample and stir for 1 minute.
- If necessary, adjust sample pH to within the range of 7 - 10 with H2SO4 or NaOH.
- Fill refilling buret bottle with silver nitrate titrant.
- Adjust solution level to 0.0 mL.
- Add 5 drops of the indicator solution to the sample.
- Titrate a blank with standard AgNO3 to a persistent light orange-red to use forend-point recognition. (A 50 mL distilled water blank giving a value of 0.2 to 0.3 mL is usual.) If the blank requires more than 0.3mL the solution in the buret may have decomposed. Refill buret and titrate another blank. Make sure blank reads appropriately beforetitrating samples.
- Titrate the sample to the same light orange-red color. Calculate ppm Cl and record with one decimal. (Be consistent in end-point recognition.)
- Dispose of samples in carboy for pick up by hazardous materials manager.
- ppm Cl- = (mL AgNO3 for sample) x N AgNO3 x 35450 / mL sample
- (mL AgNO3 for blank = 0 if sample was not diluted with distilled water. If sample was diluted, subtract value for amount of distilled water used.)
- Standard Methods for the Examination of Water and Wastewater. 1985. 16th Edition. P 286.