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Analytical Method: Calcium in soils

Photometric determination with Glyoxal-bis (2-hydroxyanil) subsequent to acid extraction

Reagents:

Cat.No. 173016  Spectroquant® VIS Spectrophotometer Prove 100 or
Cat.No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or
Cat.No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600 or
Cat.No. 109748  Spectroquant® Photometer NOVA 30 or
Cat.No. 109751  Spectroquant® Photometer NOVA 60 or
Cat.No. 173632  Spectroquant® Colorimeter Move 100
Cat.No. 114946  Rectangular cells 10 mm and/or
Cat.No. 114947  Rectangular cells 20 mm and/or
Cat.No. 114944  Rectangular cells 50 mm
Cat.No. 114815  Spectroquant® Calcium Test
Cat.No. 100316  Hydrochloric acid 25 % for analysis
Cat.No. 109970  Hydrochloric acid 1 mol/l for analysis
Cat.No. 105588  Sodium hydroxide solution 10 % for analysis
Cat.No. 109531  MColorpHastTM pH-Indicator strips pH 0 - 6
Cat.No. 116754  Water for analysis
 
Sample preparation:
In an Erlenmeyer flask mix 10 g of air-dry, finely-ground, stone-free material with 50 ml hydrochloric acid
1 mol/l and held at a gentle boil for 5 minutes on a heating plate. The pH range of the supernatant solution should be 1 - 3 (test with pH-indicator strips). If necessary, adjust by using hydrochloric acid 25 %.
Heat the material once again, for a few minutes. After cooling, adjust the mixture to pH 7 - 7.5 using a pH-meter by addition of sodium hydroxide solution 10 %. Transfer the suspension, with water for analysis, into a 1000-ml volumetric flask, fill up to the mark with water for analysis, and mix.
 
Analysis:
Determine with the above mentioned test kit.
 
Calculation:
Calcium content in mg/kg Ca = analysis value in mg/l Ca x 100

Materials

     
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