How do you use a watch glass in titration?
To observe color chg or what?
Please tell me!
Answer:
The only time I have used a watch glass in a titration is either to cover the top of the buret (if your sample in the buret is prone to oxidation you can do this - enough air will still get through so the buret will work), or to cover your samples in the ernlenmeyer flask before you titrate. Let's say that you need to do 5 titrations. You weigh out or transfer your samples to the ernlenmeyer flasks such that you have them lines up like ducks in a row on an assembly line. In order to keep crap out of the flasks, prevent evaporation, and so on, you can place watch glasses over the top of the erlenmeyer flask until you are ready to titrate your samples. These are the only two instances that I have used watch glasses for titrations. And I have done a LOT of titrations!
I agree with the previous post about observing color - a white piece of paper works best!
You don't really need a watch glass, though I have used it to do things like dividing a solid into several portions. That would be my guess. For color change, I'd recommend using a sheet of white paper.
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