pipetting

• What are the two main types of measuring pipettes?

  • Mohr Pipettes
  • Serological Pipettes
• How are Mohr pipettes calibrated?

  They are calibrated between two marks on the stem.
• What is the significance of the space between the last calibration mark and the delivery tip in Mohr pipettes?

  The volume of that space is not known and cannot be used for measuring.
• What is a characteristic feature of Mohr pipettes regarding graduation marks?

  The graduation on Mohr pipettes always ends before the tip.
• What type of pipette is generally a blowout pipet?

  Serological Pipettes
• What is the design feature of serological pipettes?

  They are long tubes with uniform diameters and graduated to the delivery tip.
• How does the orifice of a serological pipette compare to that of a Mohr pipette?

  Serological pipettes have a larger orifice than Mohr pipettes.
• What is known about the distance from the last calibration mark to the tip in serological pipettes?

  The distance is known and the graduation marks continue to the tip.
• What are the characteristics of a transfer pipet?

  • No graduation marks
  • Used to transfer solutions without consideration of a specific volume
• What is the typical volume range for a pipette used to deliver a single specific volume of liquid?

  Between 1 and 100 ml.
• Where is the bulb located in a pipette designed to deliver a specific volume?

  The bulb is located in the middle of the pipette.
• What are the two types of automatic pipets mentioned?

  • Fixed volume automatic pipet
  • Variable volume automatic pipet
• What is a micropipette used for?

  It dispenses less than 1 ml.
• What is a macropipette used for?

  It dispenses more than 1 ml.
• How does an automatic pipet create suction?

  It relies on a piston for suction creation.
• What must be done with the disposable tip of an automatic pipet?

  It must be changed for each use.
• What is the function of the piston in an automatic pipet?


  The piston does not come in contact with the liquid.
• How does the operation of an automatic pipet compare to a syringe?

  It operates by moving the piston in the pipet tip, similar to a syringe.
• What is required between samples when using an automatic pipet?

  Rinsing and blotting between samples may be required.
• What are the types of automatic pipets mentioned?

  1. Air Displacement
  2. Positive-Displacement
  3. Dispenser and Dilutor/Dispenser
• What is the purpose of a pipette bulb?

  It is used to draw liquid up into the pipette.
• What are the types of pipette bulbs mentioned?

  1. Rubber Bulb
  2. Pipet Filler
  3. Pipet Aid
  4. Pipet Pumper
• What is the meniscus in liquid measurement?

  The meniscus is the curved surface of the liquid against the glass.
• How should the pipette be held when reading the meniscus?

  The calibration mark should be at eye level.
• What are the two types of meniscus based on the solution type?

  1. Lower Meniscus - Clear Solutions
  2. Upper Meniscus - Colored or Viscous Solutions
• What is calibration in the context of laboratory glassware?

  Calibration checks the exact volume of glassware or other apparatus used in quantitative measurement.
• Which organization calibrates laboratory equipment by weight using distilled water?

  National Bureau of Standards
• What does TC stand for in calibration?

  TC stands for "to contain".
• What is the purpose of a volumetric pipet?

  It is designed to hold one exact volume of liquid.
• What is the function of Griffin and Berzelius beakers?

  They are designed to hold different volumes rather than one exact amount.
• When are graduated cylinders used?

  They are used to measure liquid when a high degree of accuracy is not essential.
• What are the types of laboratory vessels mentioned?

  • Volumetric Flasks
  • Erlenmeyer Flasks
  • Beakers
  • Graduated Cylinders
  • Pipet Aid
• What is the characteristic of liquid-in-glass thermometers?

  They use colored liquid or mercury encased in plastic or glass material.
• Why are mercury thermometers not used in laboratories or hospitals?

  They have side effects if a person is exposed to mercury.
• What temperature range do liquid-in-glass thermometers usually measure?

  Between 20 degrees to 400 degrees Celsius.
• What are the three types of liquid-in-glass thermometers?

  1. Partial Immersion
  2. Total Immersion
  3. Surface Thermometers
• What is the purpose of a partial immersion thermometer?

  It is used for measuring temperature in units such as heating blocks and water baths.
• What is the application of a total immersion thermometer?

  It is used for refrigeration applications.
• What is the function of surface thermometers?

  They are used for flat surfaces such as ovens or incubators.
• What is an advantage of electronic thermometers?

  They have a size and millisecond response time.