GB/T 30728-2014Determination of nitrogen in solid biofuels (English PDF)

4.1 anhydrous sodium carbonate

sodium carbonate purity reagent or reference standard material.

4.2

sucrose.

4.3 mixed catalyst

anhydrous sodium sulfate, sulfuric acid, mercury and chemically pure selenium powder mass ratio (64101) mixing (such as sulfuric anhydride 32g

Sodium, 5g mercury sulfate and selenium powder mixed 0.5g), finely and mix and reserve.

4.4 sulfate

density 1.84g/cm3.

4.5 ethanol

mass fraction of 95% and above.

4.6 mixed alkali solution

370g of sodium hydroxide and sodium sulfide 30g dissolved in water to prepare a solution of 1000mL.

4.7 boric acid solution

about 30g/L. 30g of boric acid dissolved in 1L of water, heated to dissolve the preparation, insoluble matter was filtered off after cooling.

4.8 Standard Solution

c 12H2SO

÷ 4 ~0.025mol/L. Preparation of standard solution of sulfuric acid. add about 40mL of water in a beaker with

Pipette 0.7mL of sulfuric acid (see 4.4) slowly added to the beaker, and then the solution was transferred to 1000mL volumetric flask, dilute with water to

Scale, thoroughly shaken evenly. Calibration standard solution of sulfuric acid. the conical flask Weigh 0.02g (weighing accuracy of 0.0002g) in advance at 130 °C

Dried to a constant mass of anhydrous sodium carbonate (see 4.1), was added 50mL ~ 60mL of water to dissolve, then add 2 to 3 drops of methyl orange indicator

Agents (see 4.9), with a standard solution of sulfuric acid titration to change from yellow to orange. Boil to expel carbon dioxide, after cooling, continue titration to orange.

According to equation (1) to calculate the concentration of the standard solution of sulfuric acid. The concentration of sulfuric acid standard solution calibration takes two people, each doing four times per repeat calibration weight 8 times

Complex calibration results poor no more than 0.00060mol/L, its arithmetic mean concentration of sulfuric acid as a standard solution, a 4-bit effective number […]