GB/T 19106-2013[GB/T 19106-2013] Sodium hypochlorite (English PDF)

5.1 General provisions

The reagents and water, which are used in this standard, refer to analytical reagents and the grade-3 water, which are specified in GB/T 6682, unless otherwise specified. The standard titration solution, impurity standard solution, preparations, products, which are used in the test, are all prepared in accordance with GB/T 601, GB/T 602, GB/T 603, unless otherwise specified.

5.2 Appearance

Observe visually under natural light.

5.3 Determination of available chlorine

5.3.1 Method summary

In an acidic medium, hypochlorite reacts with potassium iodide, to precipitate iodine. Using starch as the indicator solution, use sodium thiosulfate standard titration solution to make titration, until the blue color disappears, which is regarded as the end point. The reaction formula is as follows.

5.3.2 Reagents

5.3.2.1 Potassium iodide solution. 100 g/L. Weigh 100 g of potassium iodide;

dissolve it in water; dilute to 1000 mL; shake well.

5.3.2.2 Sulfuric acid solution. 3 + 100.Pipette 15 mL of sulfuric acid; slowly

inject 500 mL of water; cool it down; shake well.

5.3.2.3 Sodium thiosulfate standard titration solution. c(Na2S2O3) = 0.1 mol/L.

5.3.2.4 Starch indicator solution. 10 g/L.

5.3.3 Instruments

5.5.4 Analytical procedures

5.5.4.1 Drawing of standard curve

5.5.4.1.1 Pipette 0.00 mL, 2.00 mL, 4.00 mL, 6.00 mL, 8.00 mL, 10.00 mL of iron standard solution (5.5.2.5), respectively, into six 100 mL volumetric flasks.

Add 5 mL of hydroxylamine hydrochloride solution, 10 mL of acetic acid-sodium acetate buffer solution, 5 mL of 1,10-phenanthroline indicator solution, to each volumetric flask. Use water to dilute it to the mark. Shake well. Let it stand for

10 min.

5.5.4.1.2 Using water as a reference, adjust the spectrophotometer to zero.

Select an appropriate cuvette, at a wavelength of 510 nm, to measure the absorbance.

5.5.4.1.3 The absorbance of the blank solution is subtracted from the absorbance of the standard colorimetric solution. Use the mass (mg) of iron, in the 100 mL standard colorimetric solution, as the abscissa; use the corresponding absorbance as the ordinate, to draw the standard curve or regression linear equation.

5.5.4.2 Blank test

Without adding sample solution, use exactly the same analytical procedures, reagents, dosage, as the test sample solution, to carry out blank test.

5.5.4.3 Determination

Pipette 50.00 mL of sample solution A. Place it in a 100 mL volumetric flask.

Add hydrogen peroxide solution dropwise, until it does not contain hypochlorite (not make the starch-potassium iodide test paper blue). Then add 5 mL of hydroxylamine hydrochloride solution, 10 mL of acetic acid-sodium acetate buffer solution, 5 mL of 1,10-phenanthroline indicator solution. Use water to dilute it to the mark. Shake well. Let it stand for 10 min. The following shall be carried out, in accordance with the provisions of 5.5.4.1.2.

5.5.5 Result calculation

The iron content is expressed in the mass fraction of iron (Fe), w3; the value is expressed in % AND calculated according to formula (3).

Where.

m1 - The value of the mass of the specimen, in grams (g);

m2 - The value of the mass of iron, which is obtained from the standard curve

OR calculated by the unitary linear regression equation, corresponding to the absorbance of the sample solution, after subtracting the absorbance of the blank solution, in micrograms (mg).

5.5.6 Tolerance

Take the arithmetic mean of the parallel measurement results, as the measurement result. The absolute value of the difference, between the parallel determination results, is not more than 0.001%.

5.6 Determination of heavy metals

5.6.1 Method summary

Under the condition of weak acidity (pH 3 ~ 4), heavy metal ions and sulfide ions in the sample will form a brown-black precipitate. Compared with the lead standard solution, which is treated by the same method, a limit test is performed.

5.6.2 Reagents and materials

5.6.2.1 Hydrochloric acid.

5.6.2.2 Hydrogen peroxide solution. 1 + 5.

5.6.2.3 Acetic acid-sodium acetate buffer solution. pH value is about 3.

5.6.2.4 Saturated solution of hydrogen sulfide. Lead hydrogen sulfide gas into

water, which does not contain carbon dioxide, until it is saturated. Prepare this solution before use.

5.6.2.5 Sodium sulfide solution. Weigh 5 g of sodium sulfide. Dissolve it in a mixture of 10 mL of water and 30 mL of glycerol. Store it in a sealed container in the dark. It is valid for one month.

5.6.2.6 Lead standard solution. 0.1 mg/mL.

5.6.2.7 Lead standard solution. 0.01 mg/mL. Take an appropriate amount of

lead standard solution (5.6.2.6). Dilute it by 10 times. Prepare this solution before use.

5.6.2.8 Phenolphthalein indicator solution. 10 g/L.

5.6.2.9 Starch-potassium iodide test paper.

5.6.3 Instruments

General laboratory equipment and 50 mL Nessler colorimetric tube.

b - Absorption tube;

c - Absorption tube cap.

Figure 1 -- Schematic diagram of arsenic determination instrument

5.7.4 Analytical procedures

5.7.4.1 Pipette 1.00 mL of arsenic standard solution (5.7.2.6), into the conical

flask of the arsenic determination instrument. Add 5 mL of hydrochloric acid.

Add water to about 30 mL. Then add 5 mL of potassium iodide solution and 5 drops of stannous chloride. Shake well. Let it stand for 10 minutes.

5.7.4.2 Pipette 25.00 mL of sample solution A. Place it in the conical flask of the arsenic determination instrument. Add hydrogen peroxide solution dropwise, until it does not contain hypochlorite (do not make the starch-potassium iodide test paper blue). Use hydrochloric acid, to neutralize the sample solution. Add another 5 mL of hydrochloric acid. Add water to about 30 mL. Then add 5 mL of potassium iodide solution and 5 drops of stannous chloride. Shake well. Let it stand for 10 min.

5.7.4.3 Add 2 g of zinc particles, to each of the above-mentioned conical flasks.

Immediately connect the glass tubes, which contain lead acetate cotton and mercury bromide test paper. Place them in a dark place, at 25 °C, for 1 hour.

5.7.4.4 Take out the arsenic spot. The arsenic spot of the sample solution shall not be deeper than the arsenic spot of the arsenic limit standard. Standard arsenic spots shall be prepared, at the same time for each determination.

7.1 Marking

7.1.1 The packaging of sodium hypochlorite shall have a firm and clear mark, which includes. the name of the manufacturer, address, product name,

"hazardous chemicals", net content, batch number or production date, production license number and sign, this standard number, "corrosive substances" and "oxidizing substances" signs and safety labels as specified in

GB 190.For plastic barrels, plastic cans, combined packaging of plastic bottle packaging and fiberboard boxes (including corrugated cardboard boxes), there shall also be the "upward" sign, which is specified in GB/T 191.

7.1.2 Each batch of exit-factory sodium hypochlorite shall be accompanied by safety technical specifications and quality certificates. The content of the quality certificate includes. the name of the manufacturer, address, product name, the words "hazardous chemicals", net content, batch number or production date, production license number and sign, certification of product quality in accordance with this standard, this standard number.

7.2 Packaging

Sodium hypochlorite's packaging shall be implemented in accordance with the requirements of GB 19107.

7.3 Transportation

Sodium hypochlorite shall be sealed when transported; the shipping container

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