Methods and steps for determination of nitrogen, phosphorus and potassium in elemental fertilizers;
(1) Determination of Nitrogen Content in Nitrogen Fertilizer
1.？ Determination of nitrogen content in ammonium nitrogenous fertilizers such as ammonium sulfate, ammonium chloride, ammonium nitrate and ammonium bicarbonate
( 1)? Preparation of test solution
Weigh 0.5g of finely ground representative fertilizer samples and place them in 100 ml? Add about 30mL distilled water to the triangle bottle? About the addition of 10 fertilizer hydrolysis agent? Drop, shake until completely dissolved (or shake 30? Minutes), and then go to 100mL? In a volumetric flask, measure the volume with distilled water, and then filter in a dry triangular flask (discard the initial filtrate when it is not dried). ?
With 1mL? Suck 1.0mL through a straw? The filtrate is 100mL? In a volumetric flask, adjust the volume to scale with distilled water and shake it evenly to obtain the ammonium nitrogen solution to be measured.
(2)? Measuring step;
Suck 2mL distilled water (blank) 2ml distilled water+1? Drop standard stock solution of fertilizer and nutrient mixture (standard use) and 2mL solution to be tested? In three small test tubes, add:
Fertilizer ammonium nitrogen 1? Reagent 4? Descending?
Fertilizer ammonium nitrogen 2? Reagent 4? Descending?
Fertilizer ammonium nitrogen 3? Reagent 4? Descending?
Shake well, let stand for 5 minutes, then transfer to a colorimetric cup and measure on a computer:
① Turn the left wheel of the filter to set the value to 1, put the blank liquid into the light path, press the "Colorimetric" key, and the function number will be switched to 1, and press the "Adjust+"key or "Adjust-"key to make the instrument display 100%.
② Place the standard solution in the light path, press the "colorimetric" key, and the function number will be switched to 3. Press the adjustment key to make the instrument display value as 18.0.
(3) Place the liquid to be tested in the light path, and the displayed value is the ammonium nitrogen content (%) of the fertilizer. For ammonium nitrate, the measured value is × 2, which is the nitrogen content of fertilizer.
2.？ Determination of nitrogen content in nitrate nitrogen fertilizer
( 1)? Preparation of the solution to be tested: The preparation process of the solution to be tested is the same as the determination of nitrogen content of ammonium nitrogen fertilizer.
(2)? Determination step
Suck 2mL distilled water (blank) 2ml distilled water+1? Drop standard stock solution of fertilizer and nutrient mixture (standard use) and 2mL solution to be tested? In three small test tubes, add:
Fertilizer nitrate nitrogen 1 reagent 2? Descending?
Fertilizer nitrate nitrogen 2? Reagent 4? Descending?
Fertilizer nitrate nitrogen 3? Reagent 1? Drop (before dropping, you must shake vigorously or heat it in a hot water bath at 70℃ for 3? Shake it several times a minute to make the sediment fully suspended before dripping)?
Shake well, let stand for 15 minutes, then transfer to a cuvette and measure it on a computer.
① Turn the left wheel of the filter to set the value to 2, put the blank solution into the light path, press the "Colorimetric" key, and the function number will be switched to 1, and press the "Adjust+"key or "Adjust-"key to make the instrument display 100%.
② Place the standard solution in the light path, press the "colorimetric" key, and the function number will be switched to 3. Press the adjustment key to make the instrument display value as 12.0.
(3) Place the liquid to be tested in the light path, and the displayed value is the nitrate nitrogen content (%) of the fertilizer. If the fertilizer is ammonium nitrate, the measured value ×2 is the nitrogen content of ammonium nitrate fertilizer.
3.？ Determination of nitrogen content in urea
( 1)? Preparation of test solution
Weigh 0.5g ground representative fertilizer sample? In 100mL? In a triangular flask, add 5mL? Wet the fertilizer with water and add 2mL? Concentrated sulfuric acid (or directly add 5mL? Fertilizer hydrolysis agent), heat with low fire, keep shaking, stop heating after no bubbles and white smoke, and turn to 100mL after cooling? Dilute the volumetric flask with distilled water to scale, filter, and use 1mL? Suck 0.5mL filtrate with a straw (when the nitrogen content is higher than 30%, it needs to be diluted by 4? Ten thousand times) or 1mL? Suck 1.0mL through a straw? Filtrate (when the nitrogen content is lower than 30%, 2? Ten thousand times) into 100mL? In a volumetric flask, use distilled water to determine the volume as the liquid to be tested (this liquid to be tested can be used to determine the contents of phosphorus and potassium in compound fertilizer). ?
(2)? When determining ammonium nitrogen in simple fertilizer, the displayed value of standard solution concentration is adjusted to? 36 (diluted 20,000 times? 18), and the concentration of the liquid to be measured indicates the nitrogen content (%) of urea and compound fertilizer. ?
4.？ Determination of biuret content in urea
( 1)? Preparation of test solution
Weighing? 3.00g？ Urea sample (accurate to? 0.0 1g), pour it in? 100mL？ In the volumetric flask, add a proper amount of water to dissolve it, then use distilled water to adjust the volume to the scale and shake it evenly to form the liquid to be measured.
(2)? Determination step
Suck 2mL distilled water (used as blank solution), 2mL distilled water+1 biuret standard stock solution (used as standard) and 2ml solution to be tested into three small test tubes, and add them into the three test tubes in turn:
Biurea? 1? Reagent 2? be filled/suffused/brimming with
Biurea? 2? Reagent 4? be filled/suffused/brimming with
Shake well, keep the temperature at about 25℃, after 65438 05 minutes, transfer to three cuvettes for computer determination:
① Turn the left wheel of the filter to set the value to 2, put the blank solution into the light path, press the "Colorimetric" key, and the function number will be switched to 1, and press the "Adjust+"key or "Adjust-"key to make the instrument display 100%.
② Place the standard solution in the light path, press the "colorimetric" key, and the function number will be switched to 3. Press the adjustment key to make the instrument display value as 1.00.
③ Place the liquid to be measured in the optical path, and the displayed value is the biuret content in urea (%).