SN/T 1037-2020Import and export lime nitrogen inspection method (English PDF)

3.1 Take samples

Sampling in accordance with GB 6679, divide the sample stack into equally divided grids, and the grids will be no less than 20 grids when dividing large samples.

Less than 12 grids, not less than 4 grids for subdividing samples, reduce to 1 kg, save 250 g of samples, 250 g of analytical samples, and pack them in a dry seal in the bottle, indicate the batch number, production date, manufacturer name, sampler and date.

3.2 General provisions

Unless otherwise specified, the reagents used are of analytical grade, and the water is the secondary water specified in GB/T 6682.The test papers are all precision test papers. test the standard titration solution, impurity standard solution, reagents and products required in the test, unless other requirements are specified, shall be in accordance with GB/T 601, Prepared according to GB/T 602.

4.1 Method 1.Distillation Titration Method (Arbitration Method)

4.1.1 Method summary

Under the action of the catalyst, the nitrogen in the sample is completely oxidized, decomposed and turned into amine salt in concentrated sulfuric acid, which is absorbed by sulfuric acid standard solution.

Back titration with alkali standard solution to determine total nitrogen.

4.1.2 Reagents and materials

4.1.2.1 Sulfuric acid (rho=1.84 g/mL).

4.1.2.2 Sodium hydroxide solution. 40%.

4.1.2.3 Sulfuric acid standard solution. 0.1 mol/L.

4.1.2.4 Sodium hydroxide standard solution. 0.1 mol/L, see GB/T 601 for the preparation method.

4.1.2.5 Catalyst. Weigh 100 g k2SO4, 10 g CuS04 · 5 H20, 1 g selenium powder, and grind it to 80 mesh (0.175 mm) in a mortar, Contained in a dry ground bottle.

4 1.2.6 Indicator. 0.1% methyl red ethanol solution 0.5% cresol green ethanol solution (11).

4.1.3 Apparatus and equipment

4.1.3.1 Semi-automatic protein analyzer (or equivalent equipment).

4.1.3.2 Electric heating digester.

4.1.3.3 Magnetic stirrer and electromagnetic stirrer.

4.1.3.4 Acid burette.

4.1.4 Measurement procedure

4.1.4.1 Digestion

Weigh 0.1 g sample (accurate to 0.0001 g), put it into the cleaned and dried digestion tube without damage, and add a few grains with a diameter of 3 mm~ 4 mm glass beads, 6 g catalyst (4.1.2.5) and 10 mL sulfuric acid (4.1.2.1), heat digestion for 30 min (extendable 5 min~10 min).

Then cool to room temperature, add 50 mL of water to the digestion tube and mix well.

4.1.4.2 Distillation

Accurately add 25 mL of sulfuric acid standard solution (4.1.2.3) and 2~3 drops of indicator (4.1.2.6) into a 250 mL Erlenmeyer flask.

The bottle is placed on the receiving tube of the distillation apparatus, and the nozzle is immersed in the solution. Add 50 mL of sodium hydroxide solution (4.1.2.2) to the digestion tube, After 7 minutes of distillation, close the steam valve and remove the receiving flask.

4.1.4.3 Determination

Titrate the solution in the receiving bottle with sodium hydroxide standard solution (4.1.2.4), and drop it until the solution turns from purple-red to bright green as the end point.

4.1.4.4 Blank test

Except that no sample is added, all are carried out in accordance with the above-mentioned measurement steps (4.1.4.3).

4.1.5 Calculation and expression of results

The total nitrogen content in the sample is calculated by mass fraction and calculated according to formula (1).

4.1.6 Precision

The precision is shown in Table 1.

5.1 Method summary

The sample is completely decomposed in a closed container, and the content of free calcium carbide is obtained from the volume change before and after the reaction.

5.2 Materials and reagents

5.2.1 Saturated salt water. saturated salt water saturated with acetylene.

5.2.2 Graduated cylindrical funnel. 60 mL.

5.2.3 Reaction flask. 100 mL.

5.2.4 Level bottle. 250 mL.

5.2.5 Thermometer.

5.3 Test device

The test device is shown in Figure 1.

5.4 Measurement procedure

Weigh 2.000 g sample (accurate to 0.001 g) into a dry 100 mL reaction flask (5.2.3), and immediately use a thermometer (5.2.5) Tighten the bottle mouth with the stopper of the graduated separatory funnel, rotate the two-way stopcock to communicate with the measuring pipe, and wait for the air in the reaction bottle (5.2.3) to be exhausted After that, turn the two-way stopcock to communicate with the atmosphere, adjust the zero point of the gas pipe, close the piston, and transfer the cylindrical graduated funnel (5.2.2) to the reaction flask.

(5.2.3) accurately add 25 mL of saturated brine (5.2.1) saturated with acetylene, shake the reaction flask constantly to make calcium carbide (free electricity) After the acetylene generated by the reaction is stabilized in the measuring pipe, move the level bottle (5.2.4) to balance the internal and external pressures and read the gas volume and atmospheric pressure and the temperature in the reaction flask during the measurement.

5.5 Calculation results and expressions

The mass fraction of free calcium carbide in the sample is calculated as x2 and calculated according to formula (2).

5.6 Precision

The precision is shown in Table 2.

6.1 Method summary

The sample is sieved through a standard sieve, and the mass of the remainder on the sieve is determined according to the mass of the material under the sieve.

6.2 Apparatus and equipment

6.2.1 Standard sieve. 30 mesh (0.595 mm).

6.2.2 Balance. with a sense of 0.01 g.

6.2.3 Brushes.

6.2.4 Oscillator. 60 r/min.

6.3 Measurement procedure

Weigh 20.00 g sample (accurate to 0.01 g), put it into a 30-mesh (0.595 mm) standard sieve (6.2.1), and cover the sieve lid.

Place it on the shaker (6.2.4) (or shake it manually), shake for 3 min~5 min, and then weigh the remaining on the sieve.

6.4 Calculation and expression of results

The standard sieve volume meter in the sample is calculated according to formula (3).