FORD FLTM AK 109-01-2001 QUANTITATIVE ANALYSIS OF PHOSPHATES IN CLEANERS《清洁剂中的磷酸盐的定量分析》.pdf

1、 FORD LABORATORY TEST METHOD AK 109-01 Date Action Revisions 2001 01 22 Revised Editorial no technical change A. Cockman 2000 03 23 Revised Editorial no technical change A. Cockman 1990 02 14 Printed copies are uncontrolled Page 1 of 4 Copyright 2001, Ford Global Technologies, Inc. QUANTITATIVE ANAL

2、YSIS OF PHOSPHATES IN CLEANERS Application This test method is used to determine the percentage of phosphate in cleaners. It is also used to determine soluble phosphates in other materials such as phosphating solutions. Apparatus Required Erlenmeyer Flask - 250 mL Funnel - Suitable for use with filt

3、er paper Watch Glasses Graduated Cylinder - 100 mL Hot Plate Analytical Balance - Precision of +/- 0.1 mg Materials Required Hydrochloric Acid Concentrated, reagent grade. CAUTION: Corrosive Nitric Acid Concentrated, reagent grade. CAUTION: Corrosive Ammonium Hydroxide Concentrated, reagent grade. C

4、AUTION: Corrosive Potassium Nitrate Reagent grade. CAUTION: Possible fire and explosion hazard Distilled or Deionized Water 10 ppm max total dissolved solids (ASTM D 1888) Litmus Paper Filter Paper Whatman No. 42, or equivalent FORD LABORATORY TEST METHOD AK 109-01 Page 2 of 4 Copyright 2001, Ford G

5、lobal Technologies, Inc. Solutions Required Ammonium Molybdate Solution Refer to FLTM AZ 102-01 Potassium Nitrate Solution 1 % concentration Sodium Hydroxide Solution 0.1 N - refer to FLTM AZ 102-01 Hydrochloric Acid Solution 0.1 N - refer to FLTM AZ 102-01 Phenolphthalein Refer to FLTM AZ 102-01 Co

6、nditioning and Test Conditions All test values indicated herein are based on material conditioned in a controlled atmosphere of 23 +/- 2 C and 50 +/- 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. Procedure 1. Transfer a

7、n aliquot of solution equivalent to 0.0050 - 0.0075 g of P2O5 to a 250 mL Erlenmeyer flask. 2. Dilute with distilled water to make the total volume approximately 60 mL. 3. Add 20 mL of concentrated nitric acid. 4. Boil mixture on hot plate to approximately 25 % of its original volume. 5. Remove from

8、 hot plate and cool to room temperature. 6. Add concentrated ammonium hydroxide until fumes are no longer evolved. 7. Continue to add concentrated ammonium hydroxide and keep testing the solution with litmus paper until the solution is as close to neutral as possible. 8. Dilute the solution to 100 m

9、L. 9. Add 0.25 mL of concentrated nitric acid. 10. Adjust the temperature of the solution to 40 to 50 C. 11. Add 50 mL of freshly-filtered ammonium molybdate solution. FORD LABORATORY TEST METHOD AK 109-01 Page 3 of 4 Copyright 2001, Ford Global Technologies, Inc. 12. Agitate the flask by swirling t

10、o thoroughly mix the solution. 13. Allow to stand for 16 hours to complete the precipitation. Do not let stand longer than 20 hours. 14. Filter the solution through a Whatman #42 filter paper, or equivalent. 15. Wash by decantation three times with small portions of a cold 1 % potassium nitrate solu

11、tion, agitating the precipitate thoroughly and allowing it to settle. 16. Transfer the precipitate to the filter and continue washing it with small portions of cold potassium nitrate wash solution until 5 mL of the wash water turns alkaline to phenolphthalein upon adding two drops of 0.1 N sodium hy

12、droxide. 17. Return the precipitate and filter paper to the flask. Add 25 mL of distilled water and disperse the precipitate and paper in it. 18. Dissolve the precipitate in a small excess of 0.5 N sodium hydroxide. 19. Add five (5) drops of phenolphthalein indicator. 20. Titrate the excess sodium h

13、ydroxide with 0.5 N hydrochloric acid. 21. Calculate the percent of phosphate as P2O5 % P2O5 = A - B x 0.00154 x 100 C Where: A = mL of 0.5 N NaOH B = mL of 0.5 N HCl C = Weight of sample General Notes In this procedure careful attention to details of sample size and acidity are essential to achievi

14、ng accuracy! 1. If the result initially obtained suggests that the aliquot of solution analyzed contained less than 0.0050 g or greater than 0.0075 g of P2O5, re-estimate the phosphate content of the cleaner and repeat the analysis with a new sample size. 2. When the expected phosphate concentration

15、 in the sample is low, it may be necessary to prepare a solution of higher concentration than 1 % in order to meet the guidelines of Steps No. 1 and 2 in the procedure. 3. When a large amount of sample is necessary to obtain an adequate amount of yellow precipitate, complications may arise due to ot

16、her components of the cleaner. For example, a precipitate may form when the sample is boiled in nitric acid if silicates are present. Unwanted precipitates must be removed by filtering before proceeding to the next step of the procedure. FORD LABORATORY TEST METHOD AK 109-01 Page 4 of 4 Copyright 20

17、01, Ford Global Technologies, Inc. 4. If the expected phosphate concentration in the sample is high, it is desirable to prepare a dilution of a 1 % solution for sampling in order to achieve accuracy in pipetting the desired aliquot. 5. If the solution becomes basic while adding ammonium hydroxide in

18、 Step No. 7, add drops of concentrated nitric acid until the solution is as close to neutral as possible before proceeding. 6. The 0.25 mL of concentrated nitric acid in Step No. 9 may be added from an eyedropper or disposable pipette. However, a calibration measurement to determine how many drops o

19、f concentrated nitric acid are equivalent to 0.25 mL must be performed. Since the surface tension of nitric acid is much lower than that of water, 18 - 20 drops/mL cannot be assumed. General Information The following is for general information only. 1. The sample to be analyzed is boiled in nitric a

20、cid to hydrolyze all forms of phosphate to orthophosphate. 2. The solution is neutralized by adding ammonium hydroxide. 3. Ammonium molybdate solution is added to the orthophosphate in the presence of nitric acid to form a yellow precipitate containing phosphate. Reaction (1): H3PO4 + 12 (NH4)2MoO4

21、+ 21 HNO3 (NH3)3PO4 12 MoO3 + 21 NH4NO3 + 12 H2O 4. After washing the precipitate free of acid, it is dissolved in an excess of standard 0.5 N NaOH solution. Reaction (2): (NH4)3PO4 12 MoO3 + 23 NaOH NaNH4HPO4 + (NH4)2MoO4 + 11 Na2MoO4 + H2O 5. The excess NaOH is titrated with standard 0.5 N HCl sol

22、ution. 6. The amount of phosphate in the cleaner, expressed as % P2O5 , is calculated as follows: % P2O5 = (mL of 0.5 N NaOH - mL of 0.5 N HCl) x 0.00154 x 100 weight of sample This formula is obtained from the stoichiometry of Reaction (2). Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities.