Soil Microbial Ecology - Soil Molecular Ecology Laboratory

Page 57
Further example of calculations for CO 2 evolution from soil (Note: this example is not
related directly to lab exercise).
1. CO 2 evolved from the soils is absorbed into the basic solution
CO 2 + 2NaOH ⎯⎯⎯⎯⎯→ Na 2 CO 3 + H 2 O
Therefore the Eqwt of CO 2 is 2 of the Mwt. = 44/2 = 22
(Meqwt = 0.222)
2. Na 2 CO 3 + BaCl 2 ⎯⎯⎯⎯⎯⎯⎯⎯→ BaCO 3 + 2NaCl
3. HCl + unreacted NaOH ⎯⎯⎯⎯⎯→ NaCl + H 2 0
4. Milliliters of HCl used X (Normality) of HCl = Meq of HCl
5. Meq of HCl = Meq of NaOH left unreacted with CO 2
6. Milliliters of NaOH X N = Total meq of NaOH used in the Experiment.
7. Total meq NaOH - meq of NaOH left = Meq of NaOH consumed by CO 2
8. Meq of Anything = Meq of Anything else.
9. Therefore Meq of NaOH consumed by CO 2 = Meq of CO 2 evolved.
10. Meq CO 2 X Meqwt of CO 2 (0.022) = Total grams of CO 2 evolved.
11. Grams X 1,000 = mg CO 2 evolved.
12. This is mg of CO 2 evolved from 50 grams of soil.
13. Therefore mg/50 = mg/g of soil (mg of CO 2 that is)