Mohr Pipet

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Description
Preparing a Mohr Pipet
Reading the Volume from a Mohr Pipet
Transferring a Liquid with a Mohr Pipet
Additional Topics
Self Check Exercises
Simple Experiment
Related Modules
Pipet, Volumetric
Bulb, Standard
Three-way Pipet Bulb
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Transferring a Liquid with a Mohr Pipet

 

Video. Filling a pipet.


Video. Liquid transfer from a pipet.

  1. Make sure there is enough liquid in a beaker or other container to completely fill the pipet. (NEVER pipet directly from a reagent bottle or volumetric flask.)

  2. Place the tip of the pipet below the liquid's surface. Using a bulb or pump, draw the liquid into the pipet. Draw slightly more liquid than needed, but DO NOT allow the liquid to enter the bulb. Remove the bulb and place a finger over the mouth of the pipet, OR stop squeezing the suction valve. Lift the pipet from the solution and touch the tip of the pipet to the side of the container to remove any excess liquid.

    checkWhy touch the inside of the container? Answer

    Any excess liquid that might be transferred to the receiving vessel should be removed before delivering the liquid. Failure to touch-off the excess liquid will result in poor results since the volume delivered will be more than the recorded volume.

  3. Read the initial volume from the pipet. If the bottom of the meniscus is not on scale, release a small amount of the liquid until the liquid is on the scale.

  4. Slowly release the liquid into a receiving vessel (a beaker or flask) until the volume delivered is approximately the amount needed.

    checkWhy does it only need to be approximately the amount needed? Answer

    Many chemical and physical properties are dependent on the volume of the solution. So, if the volume of the liquid delivered is accurately recorded, the volume can be included in any subsequent calculation without affecting the determination.

  5. Touch the tip of the pipet to the inside of the receiving vessel to add any liquid that was to have been transferred.

    checkWhy touch the inside of the receiving vessel? Answer

    Any liquid that was released from the pipet should be transferred to the receiving vessel. Failure to transfer even small amounts of the liquid will result in poor results since the volume delivered will be less than the recorded volume.

  6. Read the final volume from the pipet.

  7. Calculate the volume delivered using the equation below.

    Vdelivered = Vinitial - Vfinal