NY/T 297-1995 Determination of total nitrogen in organic fertilizers NY/T297-1995 standard download decompression password: www.bzxz.net

Agricultural Industry Standard of the People's Republic of China
Determination of Total Nitrogen in Organic Fertilizers
1 Subject Content Scope of Application
NY/T 297-1995
This standard specifies the method for determining the total nitrogen content of organic fertilizers by digestion with sulfuric acid and hydrogen peroxide and then distillation. This standard is applicable to the determination of total nitrogen content in non-mud organic fertilizers. 2 Reference Standards
GB/T6682 Specifications and Test Methods for Water Used in Analytical Laboratories 3 Principle of the Method
The organic nitrogen in organic fertilizers is converted into ammonium nitrogen by digestion with sulfuric acid and hydrogen peroxide. The ammonia distilled out after alkalization is absorbed by boric acid solution and titrated with standard acid solution to calculate the total nitrogen content in the sample. 4 Reagents
Except for those specified, all reagents used are analytically pure. The water used for analysis should meet the specifications of Grade 3 water in Chapter 5 of GB/T6682. 4.1 Sulfuric acid (GB/T 625).
4.230% hydrogen peroxide (GB6684).
4.3Sodium hydroxide: 40% (m/V) solution
Weigh 40g sodium hydroxide (GB629 chemically pure) and dissolve it in 100mL water. 4.4Boric acid: 2% (m/V) solution
Weigh 2g boric acid (GB628) and dissolve it in 100mL of about 60℃ hot water. After cooling, use dilute alkali to adjust the solution pH to 14.5 on the acidometer. 4.5 Nitrogen determination mixed indicator
Weigh 0.5g bromocresol green (HG3---1220) and 0.1g methyl red (HG3-958) and dissolve them in 100mL 95% ethanol. 4.6 Preparation and calibration of sulfuric acid [c(1/2HzsO.) = 0.05mol/L or hydrochloric acid [e(HC1) = 0.05mol/L standard solution, in accordance with GB601.
5 Instruments and equipment
Usually used laboratory instruments and
5.1 Analytical balance: sensitivity 0.1mg.
5.2 Kelvin flask: 50mL or 100mL.
5.3 Adjustable electric furnace: 1000W.
5.4 Stoppered triangular flask: 150mlc
5.5 Acid burette: 10ml.
5.6 Small funnel with bay neck: 2cm
5.7 Nitrogen determination distillation wing: as shown in Figure 1. Approved by the Ministry of Agriculture of the People's Republic of China on November 23, 1995 and implemented on May 1, 1996
6 Preparation of samples
NY/T297-1995
Figure 1 Nitrogen determination distillation apparatus
1-Electric furnace (1kW); 2-Distillation flask (round bottom flask 1000mL+3-Rubber stopper; 4-Piston; 5-Simple funnel (50mL); 6 Nitrogen determination ball: 7-Rubber tube; 8-Spherical frosted interface or rubber stopper; 9-Condenser; 10-Ball; 1 1--Receiver (250mL Erlenmeyer flask) Take the air-dried laboratory sample and mix it thoroughly, then reduce it to about 100g by quartering, crush it, pass it through a 1mm pore size sieve, and put it into a sample bottle for later use.
7 Analysis steps
7.1 Preparation of sample solution
Weigh 0.5g of the sample (liquid fertilizer such as urine or feces can directly weigh 1~2g of liquid mass), accurate to 0.001g, and place it at the bottom of the Kelvin flask (5.2). Rinse the sample adhering to the wall of the flask with a small amount of water, and add 5. 0mL sulfuric acid (4.1), 1.5mL hydrogen peroxide (4.2), shake carefully, put a small curved funnel on the bottle mouth, and leave it overnight. Slowly heat it on an adjustable electric stove (5.3) until the sulfuric acid smokes, remove it, add 15 drops of hydrogen peroxide (4.2) after it cools slightly, shake the Kelvin flask gently, heat for 10 minutes, remove it, add 5 to 10 drops of hydrogen peroxide (4.2) in batches after it cools slightly and boil it in batches until the solution is colorless or light yellow clear liquid, continue heating for 10 minutes to remove the remaining hydrogen peroxide. Remove it and cool it slightly, Carefully add water to 20-30 mL and heat to boiling. Remove and cool, rinse the small bent-necked funnel with a small amount of water, and collect the washing liquid in the original Kelvin flask. Transfer the digestion liquid to a 100 mL volumetric flask, add water to the volume, let it stand to clarify or dry filter it with phosphorus-free filter paper into a stoppered conical flask (5.4) for later use. Perform two parallel determinations for the same test.
7.2 Blank test
Except for not adding the sample, the reagent dosage and operation are the same as those for the sample determination. 424
7.3 Determination
NY/T 297-1995
7.3.1 Before distillation, check whether the distillation apparatus is leaking, and clean the pipeline by empty distillation. 7.3.2 Aspirate 50.0mL of the unboiled clear liquid into the distillation flask (2 in the figure), and add 200mL of water. Add 10mL of boric acid solution (4.4) and 5 drops of mixed indicator (4.5) to the lower end of the condenser in a 250mL conical flask (11 in the figure), and insert the nozzle into the boric acid liquid surface. Slowly add 15mL of sodium hydroxide solution (4.3) into the distillation flask from the simple funnel (5 in the figure), and close the piston (4 in the figure). Heat and distill, and stop distillation when the volume of the distillate is about 100mL.
7.3.3 Titrate the distillate with sulfuric acid standard solution or hydrochloric acid standard solution (4.6) until the color of the distillate changes from blue to purple-red. Record the volume of the acid standard solution consumed (mL). The volume of the acid standard solution consumed in the blank determination shall not exceed 0.1mL. 8 Expression of analysis results
Total nitrogen (N) content is expressed in g/kg and is calculated as follows: (V -- V) - c X 0. 014 × D × 1 000Total nitrogen (N)bzxz.net
Wherein: V
The volume of standard acid solution consumed by the test solution titration, mL; -The volume of standard acid solution consumed by the blank titration, mL; The concentration of the acid standard solution, mol/L;
The mass of nitrogen equivalent to 1.00mL sulfuric acid (1/2H,SO.) or hydrochloric acid standard solution, expressed in grams; The multiple of fractionation, fixed volume/fractionation volume, 100/50; D
-Weighed sample mass, g;
Converted to the content per kilogram of sample.
The result should be expressed to two decimal places.
9 Tolerance
9.1 The arithmetic mean of the results of two parallel determinations shall be taken as the determination result. 9.2 The absolute difference between the two parallel determination results shall meet the requirements of the following table: Ng/kg
5.01~~10.00
Additional Notes:
This standard is proposed by the National Soil and Fertilizer Station of the Ministry of Agriculture. Allowable difference, g/kg
This standard is drafted by the National Soil and Fertilizer Station of the Ministry of Agriculture and Changsha Soil and Fertilizer Testing Center. The main drafters of this standard are He Pingan, Liu Haihe, Su Yunhui, Du Sen, and Wang Guohua. 425
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