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I am having trouble taking aliquots using the 10 ml volumetric pipette.
After rinsing, I draw the solution up past the calibration mark and stopper the pipette with my index finger. Then I slowly rotate the pipette and try to let a tiny bit of air inside to get the meniscus down to the calibration mark. But every time, the solution just shoots down, or goes just below the calibration mark.
How can I improve my technique?
If you have to stopper the pipette with your finger, it just takes practice. I believe the proper way to do it is to just roll your finger to the side very slowly, but I've heard several strategies including rotating the pipette like you said, and rocking/sliding your finger back and forth.
It is a lot easier if you have access to pipette bulbs like these, which let you squeeze the side arm to expel liquid smoothly:
These are easy to use too - you just roll it down to expel the liquid:
Most labs should have either of these, especially university ones. Maybe less common in high schools.
