（1） Instruments and reagents required for testing

1. One 1000ml brown volumetric flask, one 100ml conical flask, one 100ml brown wide mouthed flask, two 10ml pipettes, and one red tipped dropper.

2. Indicator (Red): Take 500ml of acetone solution and add a small bottle of red sample reagent to a 1000ml solvent. Stir until completely dissolved, then put it into a brown glass bottle and cover it as a substitute.

3. Detection reagent (white): Take 1000ml of distilled water and add a small bottle of white sample reagent to a 1000ml solvent. Stir until completely dissolved, then put it into a brown glass bottle and cover it as a substitute.

（2） Testing method

1. Extract 5ml of the test solution using a 10ml pipette and place it in a conical flask.

2. Take 2 drops (about 0.1ml) of indicator from a dropper and add them to a conical flask. The liquid color will turn light yellow.

3. Slowly drip the detection reagent into a conical flask using a 10ml pipette (shake the flask while dripping and observe the color change)

4. When the liquid color changes from light yellow to light orange red as the endpoint of titration, mark the consumed test agent on the pipette.

5. The number of milliliters of detection reagent consumed is the concentration of the detection solution in tens of thousands of parts (concentration ratio). If 0.05ml of detection reagent is consumed, the concentration is 0.05% (i.e. 0.005%); Such as consumption

If 0.3ml is removed, the concentration will be 0.03%; if 1.0ml is consumed, the concentration will be 0.1%; If 5.0ml is consumed, the concentration will be 0.05% (i.e. 0.5%) and so on.