Prepare Standard 1 - Hach CODmax III User Manual

4. Stir to mix. Add 0.1 g of sodium sulfate to the container.
5. When sodium sulfate is fully dissolved, dilute to 1000 mL with deionized water.

3.3.4 Prepare standard 1

Prepare 1500 mg/L standard solution (STD1).
Items to collect:
• Sulfuric acid, 95–98%, ACS, 0.5 mL
• Potassium acid phthalate, PT, 0.63765 g
• Deionized water
1. Add 400 mL of deionized water to an applicable container.
2. Use a stirrer to mix.
3. Carefully add 0.5 mL of sulfuric acid to the container.
4. Carefully add 0.63765 g of potassium acid phthalate to the container.
5. When the potassium acid phthalate is fully dissolved, dilute to 500 mL with deionized water.
Note: Dry the potassium phthalate in an oven at 105 ºC for 2 hours before use.
Use the COD standard laboratory method to determine the value of the standard solution.
Measured value must be 1500 ± 30 mg/L.
English 15