Determination of organic carbon in soil using fas
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Procedure:
Determination of Soil Organic Carbon:
Take 1 g of soil in a 500 mL conical flask.
Add 10 mL of 1N K2Cr2O7 solution and shake to mix it.
Then add 20 mL Con. H2SO4 and swirl the flask 2 or 3 times.
Allow the flask to stand for 30 minutes on an asbestos sheet for the reaction to complete.
Pour 200 mL of water to the flask to dilute the suspension. Filter if it is expected that the end point of the titration is not to be clear.
Add 10 mL of 85% H3PO4 and 1 mL of Diphenylamine indicator and back titrate the solution with 0.5 N Ferrous Ammonium Sulphate, till the colour flashes from violet through blue to bright green. H3PO4 gives sharper endpoint, by making the colour change, distinct through a flocculating effect.
Note the volume of Ferrous Ammonium Sulphate.
Carryout blank titration (without soil) in a similar manner.
i. Calculation:
% of Organic Carbon in Soil (R) is,
Where,
W - Weight of Sample
V1 - Blank Titre value
V2 - Titre value of the Sample
N - Normality of K2Cr2O7 (Here it is 1N)
C - Correction Factor (1.334, 1.724)
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Determination of Soil Organic Carbon:
Take 1 g of soil in a 500 mL conical flask.
Add 10 mL of 1N K2Cr2O7 solution and shake to mix it.
Then add 20 mL Con. H2SO4 and swirl the flask 2 or 3 times.
Allow the flask to stand for 30 minutes on an asbestos sheet for the reaction to complete.
Pour 200 mL of water to the flask to dilute the suspension. Filter if it is expected that the end point of the titration is not to be clear.
Add 10 mL of 85% H3PO4 and 1 mL of Diphenylamine indicator and back titrate the solution with 0.5 N Ferrous Ammonium Sulphate, till the colour flashes from violet through blue to bright green. H3PO4 gives sharper endpoint, by making the colour change, distinct through a flocculating effect.
Note the volume of Ferrous Ammonium Sulphate.
Carryout blank titration (without soil) in a similar manner.
i. Calculation:
% of Organic Carbon in Soil (R) is,
Where,
W - Weight of Sample
V1 - Blank Titre value
V2 - Titre value of the Sample
N - Normality of K2Cr2O7 (Here it is 1N)
C - Correction Factor (1.334, 1.724)
HOPE IT HELPS U ✌️✌️✌️
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