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Total Chloride Determination

Reagents

  1. CALCIUM OXIDE
  2. ACETIC ACID (25%) - Dilute concentrated acid with distilled water, 1:4.
  3. POTASSIUM CHROMATE INDICATOR - Dissolve 5 g K2Cr04 in 100 mL deionized water.
  4. STANDARD SILVER NITRATE TITRANT, 0.03 N - Dissolve 5.0964 g AgN03 in deionized water and carefully dilute to 1 L. This solution can be checked against a standard sodium chloride solution if desired. Store silver nitrate solution in a brown bottle and keep in the dark.

Apparatus

  1. 50 mL BURET, FUNNEL, AND STAND
  2. 1 L VOLUMETRIC FLASK
  3. 250 mL ERLENMEYER FLASKS
  4. MAGNETIC STIRRER
  5. FUNNEL, FUNNEL STAND, AND FILTER PAPER
  6. HOT PLATE AND HOT WATER

Procedure

  1. Accurately weigh 1 g of ground sample into a porcelain crucible.
  2. Add 0.25 g of calcium oxide and mix.
  3. Weigh out 0.25 g of calcium oxide into a separate crucible to serve as a blank. To each crucible add sufficient water to give a thin paste.
  4. Place sample & blk into furnace and increase temperature gradually until temperature reaches 550oC.
  5. Ash at this temperature for at least 90 min.
  6. Remove the sample & blk from the muffle furnace and cool.
  7. Add about 15 mL of hot water to the crucibles and break the ash into a fine powder.
  8. Pour the mixtures through filter paper into 250 mL Erlenmeyer flasks and rinse the crucibles with water into filter.
  9. Wash the residue in the filters with five 10 mL portions of hot water. Bring up the final volume to the 100 mL mark on the Erlenmeyer with dH20.
  10. Cool the filtrate and add dilute acetic acid dropwise until the solution is about pH 6.0 to 7.0. (Check pH with pH paper.)
  11. Cool and add 5 drops of the potassium chromate indicator to the sample and to the blank.
  12. Titrate the blank, then the sample, with standard AgN03 to a persistent light orange-red. (Be consistent in end-point recognition.)
  13. Calculate value and report with 2 decimals.
  14. Pour the waste into a carboy for pick up by the hazardous waste manager.

Calculation

  1. %Cl = ((mL AgN03 for sample - mL AgN03 for blank) X NAgN03 X 3.545)/g sample
  2. %NaCl = %Cl (1.65)