NY/T 1976-2010Water-soluble fertiliers. Determination of organic matter content (English PDF)

5.2 Electric sand bath or other heating device with the same effect: The

temperature (room temperature to 300°C) can be adjusted.

5.3 Ground Erlenmeyer flask: 200 mL.

5.4 Ground simple air condenser used with the ground Erlenmeyer flask: It is about 1 cm in diameter and about 20 cm in length.

6.1 Preparation of sample

After the solid sample has been divided for several times, take about 100 g;

quickly grind it until it passes through a 0.50 mm aperture sieve (If the sample is wet, it may pass through a 1.00 mm sieve). MIX well and place in a clean, dry container. After shaking the liquid sample several times, quickly take about

100 mL and place it in a clean, dry container.

6.2 Preparation of sample solution

6.2.1 Solid sample: WEIGH 0.5 g~1 g (accurate to 0.0001 g) of sample in a 100 mL beaker; ADD a small amount of water; USE a glass rod to grind the solid to dissolve it; TRANSFER the solution to a 100 mL volumetric flask; USE water to dilute it and mix well.

6.2.2 Liquid sample: WEIGH 1 g~2 g (accurate to 0.0001 g) of sample and place it in a 100 mL volumetric flask; USE water to dilute it and mix well.

6.3 Oxidation of sample solution

Immediately after mixing, pipette 5.0 mL of sample solution (homogeneous emulsion) into a 200 mL ground Erlenmeyer flask; ADD 5.0 mL of potassium dichromate solution (4.6) and 10.0 mL of sulfuric acid (4.3).

Connect the Erlenmeyer flask to the simple air condenser; PLACE it on an electric sand bath that has been preheated to 200°C~230°C for heating. When the first drop of condensate drops from the lower end of the simple air condenser, the time is counted. Oxidize for 10 min±0.5 min. REMOVE the flask and allow to cool. USE water to rinse the inner wall of the condenser; MAKE the volume of the solution in the Erlenmeyer flask about 120 mL.

Note: If an oil bath and a hole-shaped electric heating device are used for oxidation, it shall ensure that the heating glassware exposes at least 20 cm of the heat source and funnel is covered.

6.4 Titration

ADD 3~5 drops of phenanthroline indicator (4.5) to the Erlenmeyer flask; USE standard volumetric solution of ferrous sulfate (4.8) to titrate the remaining potassium dichromate. The color changing process of the solution reaches the end point through orange-yellow -> blue-green -> brown-red. If the volume consumed by the titration is less than 1/3 of the volume consumed by titrating the blank, it shall reduce the sample weighing quantity and re-determine.

6.5 Blank test

USE 5.0 mL of water instead of the sample solution. The other procedures are the same as the determination of the sample solution. Only when the titration absolute difference between two blank tests is <=0.06 mL, the average can be taken and substituted into the calculation formula.