1. Estimation of DO.pdf practical which is helpful for botany and zoology students

Estimation of do that is dissolved oxygen content from the given sample.. hybenjkmkre heavy leak bek train barunu f hachtini kudisi Karl irak Luzerne Krabi praveen magic menus Jango is Karyn jaurschjoonvfredvhuiknbbbhhhjjjnwnwjkwkkkoooooojhhfeedfyuijbfdthjnnnkmmkkkkkwjwjjhhgsywuiiokfdcvhtrtwyjkknbbbjbbnkutfwhjkkknbshyttfgjioookgfdvbhyiknbfdtujkoopplsssssnsnhguiekknnnm

1. Practical (4.2)

2. •Date: 7
TH
May 2022

3. •1.Estimationof(DO),BODandCOD
•2.EstimationofPO4,SO4andNO3
•3.Estimationofmajorcations–Na,K,Ca,MgandSalinity(hardness)
•4.Fieldexcursiontoanindustrialareatoassesenvironmentalimpact

4. Dissolved oxygen
•Dissolved oxygen (DO): The amount of oxygen dissolved in a unit
volume of water
•when excess organic materials, such as large algal blooms, are
decomposed by microorganisms
–Low levels of oxygen (hypoxia)
–no oxygen levels (anoxia)
•During this decomposition process, DO in the water is consumed

5. •Fluctuation in DO levels depends upon various conditions
•DO is considered an important measureto determine
–water quality
–the amount and type of biomass a freshwater system can support
–the amount of decomposition occurring in the lake or stream.
–DO levels below 1 mg/L are considered hypoxic and usually devoid of
life.

6. •Aim:ToestimatetheDissolvedOxygen(DO)inagivenwatersample
•Introduction:Theterm‘DissolvedOxygen’isusedtodescribetheamount
ofoxygendissolvedinaunitvolumeofwater.Itisessentialforthe
maintenanceofhealthylakes,rivesetc.Thepresenceofdissolvedoxygen
inwaterisgoodsign.TheminimumDOlevelof4to5mg/Lorppmis
desirbleforsurvivalofaquaticlife.
•TheD.O.ismainlyinfluencedbyadditionofpollutedwater/wastetothe
waterbody.Thewasteactsasfoodforcertainbacteriaandthusthe
concentrationofbacteriaincreases.Thisincreasedpopulationcause
declineintheamountofD.O.TheD.O.analysisplayakeyroleinwater
pollutioncontrolactivities.

7. •TwomethodsarecommonlyusedtodetermineDOconcentration:(1)The
iodometricmethodwhichisatitration-basedmethodanddependson
oxidizingpropertyofDOitisalsocalledasWinlker’smethodand(2)The
membraneelectrodeprocedure,whichworksbasedontherateof
diffusionofmolecularoxygenacrossamembrane.
•Principle:IntheIodometricmethod,divalentmanganesesolutionisadded
tothesolution,followedbyadditionofstrongalkaliinaglass-stopper
bottle.DOrapidlyoxidizeanequivalentamountofthedisperseddivalent
manganesehydroxideprecipitatestohydroxidesofhighervalencestates.
Inthepresenceofiodideionsinanacidicsolution,theoxidized
manganeserevertstothedivalentstate,withtheliberationofiodine
equivalentoftheoriginalDOcontent.Theiodineisthentitratedwitha
strandedsolutionofthiosulfate.Thetitrationendpointcanbedetected
visuallywithastarchindicator.

9. •Requirements:
•A. Chemicals:
–Manganese sulfate: MnSO
4
–Alkali-iodide-azide
–Concentrated sulfuric acid: Conc. H
2SO
4
–Starch solution
–Sodium thiosulfate: Na
2S
2O
3
•B. Apparatus:
–Stoppard bottle, pipettes, Conical flask, beaker, burette,
burette stand.

10. •Preparation of Chemicals
–MnSO
4 : Dissolve 24 g of MnSO
4in 50ml of dist. Water
–Alkali azide reagent: 35 g of KOH + 8 g of KI dissolve in 50ml of dist. Water
–Starch indicator: 1 g of starch dissolve in 50ml of hot water
–Na
2S
2O
3(0.025N): 6.25 g of Na
2S
2O
3dissolve in 1 Lit. of dist. Water

11. •Procedure:
•Take300(full)mlofwatersampleinstopperedbottle
•Add2mlofMnSO4and2mlofAlkaliazidereagenttothereagentbottles
(stopperedbottles)
•Ifoxygenispresent,abrowninsh-colourcloudofprecipitatewillappear.
•Allowittosettleforsufficienttimeinordertoreactcompletelywith
oxygen.
•Add2mlofConc.H
2SO
4viapipette.
•Carefullystopperandinvertseveraltimestodissolvetheppt.
•Nowtake50mlofthesampleintoaconicalflaskandadd2-3dropsof
starchindicatorandtitrateitagainstNa
2S
2O
3
•Thebluishcoloredcomplexbecomescolourlessattheendpointof
titration.
•RecordthereadingscancalculateDOusingformula.

12. •https://www.youtube.com/watch?v=m9XGsEs
55Qo

13. Formula to calculate DO
V1 = Burette reading
V2 = Volume of sample bottle
V3 = Volume of MnSO4 + Alkali reagent (2+2)=4 ml
V4 = Volume of sample taken for analysis