Biological oxygen demand (BOD) of water sample analysis.

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Biological oxygen demand (BOD) of water sample analysis

Data collection

Pipette solution

Sample A: Fish pond water fixed on the day of collection (50cm³)

Sample B: Fish pond water fixed three days after collection (50cm³)

Burette solution

Sodium thiosulphate (0.0250mol/dm³)

My results:

Sample A

Sample B

Trial 1

Trial 2

Trial 1

Trial 2

Burette readings (cm³) ±0.10cm³

Initial

0.00

4.00

8.00

10.30

Final

2.90

7.00

10.30

12.60

Total

2.90

3.00

2.30

2.30

Mean

2.95

2.30

Qualitative data:

- Collected sample was very murky

- The first end point colour was of a yellow colour, perhaps not light enough

- Addition of starch indicator produced a grey-black solution; perhaps did not add enough indicator, however this did not pose as a problem

- There was one occasion where I suspected to have added too much sodium thiosulphate, however the second trial indicated that I did not go past the end point too much

Calculations

To calculate the dissolved oxygen