GB/T 2367-2016Sodium nitrite for industrial use (English PDF)

4.1 Appearance

White or microstrip light yellow crystals.

4.2

The sodium nitrite for industrial shall be tested with the methods specified in this standard, which shall meet those specified in Table 1.

Table 1

Item Index

Superior product First-grade product Acceptable product

Sodium nitrite (NaNO2) (by dry basis), omega/% >= 99.0 98.5 98.0

Nitratine (by dry basis), omega/% <= 0.8 1.3 -

Chloride (by NaCl) (by dry basis), omega/% <= 0.10 0.17 -

Insoluble matter (by dry basis), omega/% <= 0.05 0.06 0.10

Moisture, omega/% <= 1.4 2.0 2.5

Looseness a (by non-caking), omega/% >= 85 a The looseness index is the item controlled by adding anti-caking agent, which shall be inspected when required by users.

5.1 General requirements

The reagents and water used in this standard refer to analytical reagents and the tertiary water specified in GB/T 6682 when no other requirements are specified. The standard titration solutions, preparations and products used in the test are prepared according to the regulations of HG/T 3696.1 and HG/T 3696.3 when no other requirements are specified.

5.2 Appearance inspection

Under natural light, the appearance is judged by visual method on the surface dish or white porcelain plate of white substrate.

5.3 Determination of sodium nitrite content

5.3.1 Method summary

In acidic solution, sodium nitrite is oxidized with potassium permanganate. The sodium nitrite content is calculated according to the consumption of potassium permanganate standard titration solution.

5.3.2 Reagent

5.3.2.1 Sulfuric acid solution

1+29. After preparing the sulfuric acid solution in proportion, heat it to about 70°C, drop potassium permanganate standard titration solution until the solution is light pink, and cool it.

5.3.2.2 Sulfuric acid solution

1+5. After preparing the sulfuric acid solution in proportion, heat it to about 70°C, drop potassium permanganate standard titration solution until the solution is light pink, and cool it.

5.3.2.3 Potassium permanganate standard titration solution

c(1/5KMnO4)~0.1 mol/L.

5.3.2.4 Sodium oxalate standard titration solution

c(1/2Na2C2O4) ~0.1 mol/L per unit. The keeping time shall not more than 30d. The preparation, calibration and calculation shall be conducted according to the following methods:

a) Preparation: weigh about 6.7g of sodium oxalate and dissolve it in 300 mL of sulfuric acid solution (5.3.2.1), dilute it to 1000 mL with water and shake well.

b) Calibration: pipette 30.00 mL-35.00 mL of sodium oxalate titration solution [c (1/2Na2C2O4)~0.1 mol/L], add 100 mL of sulfuric acid solution (8+92), titrate it with potassium permanganate standard titration solution, heated it to 65°C near the end point, and continue titrating it until the solution is light pink for 30s. Carry out the blank test at the same time.

c) Calculation: the accurate value (c) of the concentration of sodium oxalate standard titration solution, in mol/L, is calculated using Equation (1):

(1) where,

V1 - - the volume of potassium permanganate standard titration solution consumed during titration, mL;

V2 - - the volume of potassium permanganate standard titration solution consumed during titration blank test, mL;

c1 - - the accurate concentration of potassium permanganate standard titration solution, mol/L;

V - - the volume of sodium oxalate standard titration solution pipetted for calibration, mL.

5.3.3 Analytical procedures

5.3.3.1 Preparation of test solution

Weigh 2.5g-2.7g of the specimen, accurate it to 0.000 2g, place it in a 250 mL beaker, and dissolve it with water. Transfer all to a 500 mL (V3) volumetric flask, dilute it to the scale with water, and shake well.

5.3.3.2 Determination

Drop about 38 mL-40 mL of potassium permanganate standard titration solution with a burette in a 300 mL conical flask. Add 25 mL (V4) of test solution with a pipette, add 10 mL of sulfuric acid solution (5.3.2.2) and heat it to 40°C. Add 10 mL (V2) of sodium oxalate standard titration solution with pipette, shake continuously to become clear solution, then heat it to 70°C -80°C, titrate it with potassium permanganate standard titration solution until the solution is light pink and does not disappear for 30s.

5.3.4 Result calculation

The sodium nitrite content is calculated as the mass fraction omega1 of sodium nitrite (NaNO2) using Equation (2):