Calculations of the Winkler Method Explained

[CGallin]

So I'm having a hard time finding exactly what calculations are involved in the Winkler method

What I have is three different titrations a;
1) Standardization of the Thiosulfate Solution which was done with deionized water
2) Blank Determination
3) Thiosulfate Titration of the Sample that I am attempting to find the dissolved oxygen content in.

The problem I am having is relating these three together. If someone could explain it to me or point me to a website that could explain this to me I would be very grateful.

Thanks

 

[Borek]

Start finding out what reactions are taking place. Google is your friend.

 

[CGallin]

Okay, so I've found the dissolved oxygen concentration (I believe) but the thing that is confusing me is why I have a Blank determination. I feel as tho I should of used this somewhere along the way but it never factored into my calculations.

 

[Borek]

Do the calculations for your blank - do they yield zero? If not, that's by how much off your final result is.

 

[CGallin]

So for the blank I have it that I used 0.3 mL of thiosulfate so I would subtract 0.3 mL from the amount of thiosulfate used in the calculations to determine the dissolved oxygen concentration?

 

[Borek]

Yes. Blank tells you how much titrant is consumed before your sample starts to react.

 

[CGallin]

Thanks for the help, i got it all figured out.