T/QAS 005-2019 Rock salt brine determination of chloride content by AgNO3 method

Scope

Main technical content: In a neutral or near-neutral solution, chloride ions react with silver nitrate to form a silver chloride precipitate. The excess silver nitrate reacts with potassium chromate to form red silver chromate, indicating the endpoint. The concentration of chloride is calculated based on the consumed volume and concentration of silver nitrate solution. 4 Reagents and materials: Unless otherwise specified, all reagents used in the analysis are of ultra-high purity grade and meet the requirements of GB/T 6682 for analytical laboratory water. - a) Nitric acid: ρ(HNO3) = 1.42 g/mL; - b) Nitric acid: 0.05 mol/L; - c) Hydrogen peroxide (ultra-high purity); - d) Hydrogen peroxide (1+9); - e) Sodium hydroxide (ultra-high purity); - f) Sodium hydroxide solution: 0.05 mol/L; - g) Potassium chromate (ultra-high purity); - h) Silver nitrate (ultra-high purity); - i) Phenolphthalein (ultra-high purity); - j) Sodium chloride (ultra-high purity); - k) Phenolphthalein indicator (1 g/L); - l) Potassium chromate solution: Weigh 5 g of potassium chromate (g), dissolve it in 80 mL of water, add a small amount of silver nitrate standard solution (n) until a brick-red silver chromate precipitate appears. Filter the solution, dilute it with water to 100 mL, and shake well. - m) Sodium chloride standard solution: c(NaCl) = 0.05 mol/L. Weigh 2.9221 g of ultra-high purity sodium chloride (j), which has been calcined at 500–600 °C for 1 hour, into a 250 mL beaker. Add water to dissolve it, then transfer it to a 1000 mL volumetric flask and dilute it with water to the mark, shaking well. - n) Silver nitrate standard solution: c(AgNO3) = 0.05 mol/L. Weigh 8.5 g of silver nitrate (h) and dissolve it in water. Transfer it to a 1000 mL brown volumetric flask and dilute it with water to the mark, shaking well. - o) Standardization: Pipette 25.00 mL of sodium chloride standard solution (m) into a 250 mL conical flask, add 25 mL of water and 0.5 mL of

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