HG/T 3811-2006Bromides for industrial use - Test methods (English PDF)

3.1 Safety warning

Some reagents used in this test are poisonous or corrosive. Special attention must be paid during operation! If splashed to skin, wash with plenty of water. If the condition is severe, take the injured to hospital for professional medical treatment.

3.2 General stipulations

Unless otherwise specified, all the reagents used in this standard refer to analytic reagents; water is Grade-3 water as stipulated in GB/T 6682. Unless otherwise specified, all the standard titration solutions, standard impurity solutions, preparations and products used in the test shall be in accordance with HG/T 3696.1, HG/T 3696.2 or HG/T 3696.3 for preparation.

3.3 Determination of bromide content

3.3.1 Potentiometric titration (arbitration)

3.3.1.1 Method summary

Under the nitric acid condition, add the starch indicator; use 216-type silver electrode as the indicating electrode, 217-type double salt bridge saturated calomel electrode as the reference electrode; use the standard silver nitrate solution for titration.

3.3.1.2 Reagent

3.3.1.2.1 Nitric acid solution. 1+4.

3.3.1.2.2 Standard silver nitrate titration solution. c(AgNO3), about 0.1 mol/L.

3.3.1.2.3 Starch solution. 10g/L (prepared before use).

3.3.1.3 Instruments

3.3.1.3.1 216-type silver electrode.

3.3.1.3.2 217-type double salt bridge saturated calomel electrode.

3.3.1.4 Analytical procedure

Take 0.4g of sample, accurate to 0.01g, into a 250ml beaker. Add 100ml of water for dissolution; add 10ml of nitric acid and 10ml of starch indicator solution. Use 216-type silver electrode as the indicating electrode; use 217-type double salt bridge saturated calomel electrode as the reference electrode. The standard silver nitrate titration solution is used for titration. At the early stage of titration, add a certain amount of standard silver nitrate titration solution. When approaching the end-point, gradually add 0.1ml per time (increased if necessary). Record the total volume and the corresponding potential E after each addition of silver nitrate. Calculate the difference delta 2E between the continuously increased potentials, delta 1E and delta 1E. The maximum value of delta 1E is the titration end-point; after the end-point, continue to record an additional potential value E.

The data record format and the calculation of the volume of the consumed standard titration solution (V) when reaching the titration end-point are shown in annex A.

3.3.1.5 Result calculation

Bromide content is counted by the mass fraction w1, its value is expressed by %, calculated in accordance with formula (1). m - the mass of specimen, unit. g; M - the molar mass of bromide, unit. g/mol; K - the coefficient to convert chloride to bromide; omega 2 - the mass fraction of chloride, unit. %.

3.4 Determination of chloride content

3.4.1 Warning. When determining chloride, sample pre-treatment requires bromine evaporation. This product is toxic, it must be carried out in the well-ventilated fume cupboard.

3.4.2 Potentiometric titration (arbitration method)

3.4.2.1 Method summary

Use nitric acid to oxidize bromide ion to bromine; and heat it for evaporation. Under the nitric acid condition, add the starch indicator; use 216-type silver electrode as the indicating electrode; use 217-type double salt bridge saturated calomel electrode as the reference electrode. Use standard silver nitrate titration solution for titration.

3.4.2.2 Reagent

3.4.2.2.1 Nitric acid solution. 2 + 3.

3.4.2.2.2 Starch solution. 10g/L (prepared before use).

3.4.2.2.3 Standard silver nitrate titration solution. c(AgNO3), about 0.05 mol/L or 0.02 mol/L.

3.4.2.3 Instruments

3.4.2.3.1 216-type silver electrode (silver electrode vulcanized);

3.4.2.3.2 217-type double salt bridge saturated calomel electrode.

3.4.2.4 Analytical procedure

Take about 4g of sample, accurate to 0.01g, into in a 250ml beaker. Add 50ml of nitric acid solution; put it in the water bath (80°C) in the fume cupboard. Heat the beaker until the yellow color fades away. Use a small amount of water to wash the beaker wall; continue to heat the beaker for 15min; wait for cooling down; then, add water to 50ml in the beaker. Add 10ml of starch indicator solution; use 216-type silver electrode as the indicating electrode and 217-type double salt bridge saturated calomel electrode as the reference electrode; use standard silver nitrate titration solution for titration. At the early stage of titration, add a certain amount of standard silver nitrate titration solution. When approaching the end-point, gradually add 0.1ml per time (increased if necessary). Record the total volume after each addition of silver nitrate and the corresponding potential E.

Calculate the difference delta 2E between the continuously increased potentials, delta 1E and delta 1E.

The maximum value of delta 1E is the titration end-point; record an additional potential value Use water to wash the wall of flask; heat it in water bath for 15min. After it is cooled, transfer it to a 250ml volumetric flask. Dilute it by adding water to the scale; shake it. Use the transfer pipette to transfer 10ml of solution into a 50ml colorimetric tube; dilute it by adding water to 25ml. Add 1ml of nitric acid and 1ml of silver nitrate solution; dilute it by adding water to 50ml; mix it evenly. The turbidity the solution generates shall not exceed that of the standard chloride turbidimetric solution.

Preparation of standard chloride turbidimetric solution. use the transfer pipette to transfer the standard chloride solution, that is prepared in accordance with the chloride content as stipulated in the product standard, into a 125ml conical flask. Handle the same procedure as the test solution.

3.5 Determination of sulfate content

3.5.1 Method summary

Under acid condition, add barium chloride and sulfate radical to generate sedimentation. Use the visual turbidimetry method for determination.

3.5.2 Reagent

3.5.2.1 Anhydrous ethanol.

3.5.2.2 Hydrochloric acid solution. 1 + 3.

3.5.2.3 Stannous chloride solution. 400g/L.

3.5.2.4 Barium chloride dihydrate solution. 100g/L.

3.5.2.5 Standard sulfate solution. 0.10mg of sulfate (SO4) per 1ml of solution. […]