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| This method determines the percent of potash in fertilizers by atomic absorption spectrophotometry.
| | <b>TM-28 was deleted May 26, 2023.</b> |
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| ==106.3.2.28.1 Reagents and Apparatus==
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| a) Atomic Absorption Spectrophotometer conforming to the specifications set forth in ASTM C114.
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| b) Potassium Chloride - KCl, Reagent Grade, dried at 105-110°C for several hours prior to use. | |
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| c) Lanthanum Oxide – La<sub>2</sub>0<sub>3</sub>, Reagent Grade.
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| d) Hydrochloric Acid - HCl, Sp. Gr. 1.19.
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| ==106.3.2.28.2 Preparation of Standard Solutions==
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| Lanthanum stock solution: Weigh 23.46 g of La<sub>2</sub>0<sub>3</sub> into a 600 ml beaker and add 400 ml H<sub>2</sub>O. While stirring add 40 ml HCl. Warm and stir on a magnetic stirrer until solution is complete. Cool to room temperature, filter into a 1000 ml volumetric flask, and dilute to volume.
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| KCl standard solution: Weigh 2.5000 g KCl into a 250 ml volumetric flask. Add approximately 150 ml H<sub>2</sub>O and boil for 30 minutes. Cool and dilute to volume. Pipette 50 ml of this solution into a 500 ml volumetric flask, add 50.00 ml of the Lanthanum stock solution, and dilute to volume. This solution is 63.18% K<sub>2</sub>0.
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| Blank solution: Pipette 50 ml of the Lanthanum stock solution into a 500 ml volumetric flask and dilute to volume. This solution is used to set the zero point on the instrument.
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| ==106.3.2.28.3 Procedure==
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| Weigh 2.4900 to 2.5000 g of the sample into a 250 ml volumetric flask, add approximately 150 ml H<sub>2</sub>O and boil 30 minutes. Cool to room temperature, dilute to volume, and let stand approximately 3 hours. Transfer a 10.00 ml aliquot to a 100 ml volumetric flask, add 10.00 ml of the Lanthanum stock solution and dilute to volume.
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| Calibrate the instrument using the Blank solution and the KCl standard solution, then determine the concentration of the sample solution.
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| ==106.3.2.28.4 Calculations==
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| The method of calculating the % K<sub>2</sub>0 will vary according to the make and model of instrument used.
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| Report the results, to the nearest 0.1%, as follows: % Potash (K<sub>2</sub>0).
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| [[Category:106.3.2 Material Inspection Test Methods]] | | [[Category:106.3.2 Material Inspection Test Methods]] |
TM-28 was deleted May 26, 2023.