https://epg.modot.org/index.php?title=106.3.2.55_TM-55,_Determination_of_Calcium,_Magnesium_and_Potassium_in_Soils&feed=atom&action=history106.3.2.55 TM-55, Determination of Calcium, Magnesium and Potassium in Soils - Revision history2024-03-28T20:56:44ZRevision history for this page on the wikiMediaWiki 1.33.1https://epg.modot.org/index.php?title=106.3.2.55_TM-55,_Determination_of_Calcium,_Magnesium_and_Potassium_in_Soils&diff=23440&oldid=prevSmithk: Per CM, article moved to conform with Sec 106. Old EPG 106.7.55 had no appreciable history and 959 hits2010-06-30T20:40:07Z<p>Per CM, article moved to conform with Sec 106. Old EPG 106.7.55 had no appreciable history and 959 hits</p>
<p><b>New page</b></p><div>This method determines the pounds per acre of exchangeable calcium, magnesium and potassium in soils by atomic absorption spectrophotometry.<br />
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==106.3.2.55.1 Reagents and Apparatus==<br />
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1) An Atomic Absorption Spectrophotometer.<br />
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2) Acetic Acid (HC<sub>2</sub>H<sub>3</sub>O<sub>2</sub>), 95.5%, 1.05 specific gravity.<br />
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3) Ammonium Hydroxide (NH<sub>4</sub>OH), 0.90 specific gravity.<br />
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4) Hydrochloric Acid (HCl), 1.42 specific gravity.<br />
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5) Lanthanum Oxide (La<sub>2</sub>O<sub>3</sub>), low calcium grade.<br />
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6) Calcium Carbonate (CaCO<sub>3</sub>), primary standard grade, dried at 105-110 ºC for several hours prior to use.<br />
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7) Potassium Chloride (KCl), reagent grade, dried at 105-110 ºC for several hours prior to use.<br />
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8) 1000 ppm Magnesium Stock Solution. This solution can be purchased from a number of sources, or it can be prepared in the laboratory from a suitable pure magnesium salt.<br />
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==106.3.2.55.2 Preparation of Extracting Solution (1N NH<sub>4</sub>OAc @ pH 7.0)==<br />
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Pour 58 mL of acetic acid into approximately 500 mL of distilled water. Add 70 mL NH<sub>4</sub>OH and mix. Dilute to approximately 950 mL and cool. Adjust the pH to 7.0 ± 0.05 with acetic acid or NH<sub>4</sub>OH. Dilute to 1000 mL with distilled water.<br />
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==106.3.2.55.3 Preparation of Standard Solutions==<br />
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Lanthanum Stock Solution (10% La): Weigh 117.28 g of La<sub>2</sub>O<sub>3</sub> into a 600-mL beaker and add 400 mL distilled water. While stirring, slowly add 500 mL HCl. Stir until solution is complete. Cool, transfer to a 1000-mL volumetric flask, and dilute to volume.<br />
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Ca, Mg and K Standard Solution: Weigh 0.5619 g dried CaCO3 into a 500-mL volumetric flask, dissolve in a minimum amount of HCl and add 0.0286 g dried KCl. Pipette a 25-mL aliquot of 1000 ppm Mg stock solution into flask and dilute to volume with distilled water.<br />
Pipette a 2-mL aliquot of this stock solution into a 100-mL volumetric flask. Add a 2-mL aliquot of 1N NH<sub>4</sub>OAc extracting solution, a 2-mL aliquot of 10% La solution, and dilute to volume with distilled water. This solution is 9.0 ppm Ca (equivalent to 9000 lbs./acre Ca), 1.0 ppm Mg (equivalent to 1000 lbs./acre Mg), and 0.60 ppm K (equivalent to 600 lbs./acre K).<br />
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Note: If necessary, the range for Ca, Mg and K can be extended by preparation of a second standard prepared as follows:<br />
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:Pipette a 4-mL aliquot of the Ca, Mg and K stock solution into a 100-mL volumetric flask, adding a 2-mL aliquot of 1N NH<sub>2</sub>OAc extracting solution, a 2-mL aliquot of 10% La solution and diluting to volume with distilled water. This solution is 18.0 ppm Ca (equivalent to 18,000 lbs./acre Ca), 2.0 ppm Mg (equivalent to 2000 lbs./acre Mg), and 1.20 ppm K (equivalent to 1200 lbs./acre K).<br />
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Blank Solution: Pipette a 2-mL aliquot of 1N NH<sub>4</sub>OAc extracting solution and a 2-mL aliquot of 10% La solution into a 100-mL volumetric flask and dilute to volume with distilled water.<br />
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==106.3.2.55.4 Procedure==<br />
Place 1 g of soil into a 20-mL scintillation vial or other suitable container. Add 10 mL of extracting solution and shake for 5 minutes. Filter on Whatman #2 paper or equivalent. Pipette a 2-mL aliquot of the filtrate into a 100-mL volumetric flask, add a 2-mL aliquot of 10% La solution and dilute to volume with distilled water. Calibrate the instrument using the Blank Solution and the Ca, Mg or K Standard Solutions, then determine the concentration of the Sample Solution.<br />
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==106.3.2.55.5 Calculations==<br />
The method of calculating the lbs./acre of Ca, Mg and K will vary according to the make and model of instrument used.<br />
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Report the results to the nearest lb./acre as follows:<br />
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:Pounds per Acre Calcium (Ca)<br />
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:Pounds per Acre Magnesium (Mg)<br />
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:Pounds per Acre Potassium (K)<br />
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[[Category:106.3.2 Material Inspection Test Methods]]</div>Smithk