1. Sample pretreatment

Weigh approximately 5g of the sample, accurate to 0.0001g, and place it in a 250mL beaker. Add 20mL of water and stir until the sample is completely dispersed. Then, add 25mL of nitric acid (1+1) under stirring to ensure that the cement sample does not contain unreacted solid particles. Dilute with water to 100mL, add 2mL of chloride ion standard solution and 2mL of hydrogen peroxide, cover with a petri dish, heat and boil, and let it boil slightly for 1-2 minutes. Cool to room temperature.

2. Measurement process

1) Instrument preparation:

ZDCL-1 automatic chloride ion potentiometric titrator

Electrode: a) pCl-1-01 chloride ion electrode

b) 217-01 Double Salt Bridge Reference Electrode

2) Reagent preparation:

Nitric acid (1+1)

hydrogen peroxide

Chlorine ion standard solution

Silver nitrate standard titration solution

3) Operation steps

Calibration of AgNO3 standard titration solution: Take 10.00mL of chloride ion standard solution and place it in a 250mL beaker. Add 2mL of nitric acid (1+1), dilute with water to about 150mL, and place it on a ZDCL-1 chloride ion automatic potentiometric titrator to titrate to the endpoint.

Blank titration: Take 2.00mL of chloride ion standard solution, place it in a 250mL beaker, dilute with water to 100mL, add 2mL of nitric acid (1+1) and 2mL of hydrogen peroxide, cover with a petri dish, heat and boil, and simmer slightly for 1-2 minutes. Cool to room temperature, rinse the surface dish and glass rod with water, add a magnetic stirrer, and place it on the ZDCL-1 automatic chloride ion potentiometric titrator for titration until the endpoint.

Sample analysis: Rinse the surface dish and glass rod with water and add one sample to the pre treated sample that has been cooled to room temperature

Place the magnetic stirrer on the ZDCL-1 chloride ion automatic potentiometric titrator and titrate to the endpoint.

matters needing attention

1) Add 25mL of nitric acid (1+1) under stirring, so that the cement sample does not contain unreacted solid particles. If there are unreacted solid particles, it will cause inaccurate measurement results.

2) During the heating process, attention should be paid to protection during operation. The operation should be carried out in a fume hood so that the generated gas and acid mist can be discharged in a timely manner.