oxygen-sensitive meter (1 Viewer)

[crammy90]

ive got its an electrochemical cell (galvanic) with pT and Ag eletrodes in KCl; all in a porous plastic membrane filter. Oxygen diffuses through the pores into the KCl and electrolysis takes place and amount(electrolysis) is directly proportional to concentration oxygen.
Is the electrolysis the O2 --> 0 + 0?
and if its a galvanic cell doesnt i dont understand how this works because Pt is inert and Ag is less reactive than K so it wouldnt displace it?
and if when the reaction occurs would the Ag run out and then the meter unusable?

 

[syriangabsta]

we need to know how the oxygen-sensitive meter works? isnt it used for measuring the concen of dissolved oxygen?

 

[tommykins]

i dont thjink we need to know how a DO probe works..

 

[syriangabsta]

Awesome. I didnt think the dot points specifically asked on how measuring techniques work

 

[crammy90]

alrite nice

 

[JasonNg1025]

Whew. Scared me for a second there...
I think we just need to know the tests, not how they work...
Wait, what's the winkler method again? I remember it's something to do with DO

 

[qqmore]

Winkler Method (Titration) for testing the quantitative amount of DO in a sample.
Note: the method involves fixing the amount of DO in a sample and determining the DO by titration later on.
1. Manganese (II) ions and hydroxide ions are added to the water sample. The amount of insoluble brown manganese (IV) oxide produced depends on the amount of DO present:
(Mn2+) + (4OH-) + (O2) --> (2MnO2) + (2H2O)

2. Acidified Iodide solution are added to react with MnO2, producing a yellow iodine solution.

3. The iodide solution released is titrated against a standard sodium thiosulphate solution from a burette containing starch indicator. The starch indicator forms a blue colour with iodinem and it disappears at the end point.
(2I2) + (4S2O3 2-) --> (4I-) + (4S2O3 2-)

4. It can be seen that each dissolved O2 molecule gives 2MnO2, giving 2I2 which reacts with 4S2O3 2- . Thus, for each molecule of thiosulphate used, at the endpoint of the titration, there was 1/4 moles of DO in the original sample.