While doing titrations, we are instructed to use pipette and they demonstrated how to use a pipette. But still after all this, we face difficulties of how to take precise reading from pipette. Example-

  1. Due to the concave water meniscus, until where to take the reading ?
  2. Is it really important to take every single drop of solution from pipette ? as while putting solution in beaker we see little bit drop left inside pipette.
  3. And what's the best way to hold pipette to avoid breaking it and easy to see the reading which we are taking ?

1 Answer 1

  1. The bottom of the meniscus (in the middle) is your measurement point and should lie on the line that you are trying to read.

  2. This is completely dependent on the type of pipette that you are using. Some pipettes are designed so that you just leave the last drop and some you are supposed to just touch the tip of the pipette to the surface of what you've dispensed already to get the last bit. TD pipettes stand for "to deliver" (leave the last bit). TC pipettes stand for "to contain" (take the last bit out).

  3. Again, this is dependent on the pipette. If you have a classic bulb pipette then you shouldn't hold it by the bulb as it is the weakest part and that's how you end up with glass in your hand.

  • 1
    $\begingroup$ Also if you have to take the last bit of liquid out you don't have to blow but just close off the top end of the pipette with your finger and the gently hold the bulb with your palm and let it heat up with the warmth of your hand. This will let the last drop fall out. $\endgroup$
    – Papul
    Jun 7, 2015 at 16:50
  • $\begingroup$ @Papul That was something new which I just got to know. And its really helpful. :D $\endgroup$
    – Shashank
    Jun 8, 2015 at 14:43
  • $\begingroup$ @ShashankSharma Yeah I saw this on YouTube somewhere. Felt like an idiot blowing the pipette all these years. $\endgroup$
    – Papul
    Jun 8, 2015 at 14:45

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