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Zentrales Analytisches Labor

Sample Preperation

Loading of the exchanger complex with NH4+ and re-exchange with Mg2+

Materials

  • PE wide-mouth bottles of 100 mL
  • Filtering funnel and blue ribbon filter
  • 50 mL pipettes
  • 200 mL and 250 mL measuring flasks
  • Shaker
  • Burette
  • 0.5 N NH4Cl solution
  • 0.2 N MgCl2 solution
  • 2% AgNO3 solution (corrosive, R: 34; S: 26-45)

Loading of the exchanger complex with NH4+-Ionen, extraction of the filtrate (1)

  • Weigh 2.5 g of air-dried fine soil and place it in a 100 mL PE-bottle with 50 mL of the 0.5 N NH4Cl extraction solution.
  • Place the suspension on the shaker for one hour.
  • Filter with distilled water in a funnel with a blue ribbon filter, pour away the percolate water.
  • Filter till no Cl- can be detected (examination with a 2% AgNO3 solution). Then filter in a 200 mL measuring flasks and fill up with distilled water.
  • The filtrate (1) is kept at 5 °C for the determination of the exchanged cations.

Re-exchange of the NH4+-ions against Mg2+-Ionen, production of the filtrate (2)

  • Wash 10 times the soil on the filter with 25 mL of a 0.2 N MgCl2 solution in 250 mL measuring flasks. The measuring flask is filled up to the mark with a 0.2 N MgCl2 solution.
  • Keep the filtrate (2) at 5 °C for the determination of re-exchanged NH4+-ions.