Graduated cylinder

graduated cylinder

A graduated cylinder, measuring cylinder or mixing cylinder is a common piece of laboratory equipment used to measure the volume of a liquid. It has a narrow cylindrical shape. Each marked line on the graduated cylinder represents the amount of liquid that has been measured.

Materials & Structure

different types of graduated cylinder: 10ml, 25ml, 50ml and 100ml graduated cylinder
A diagram of two upright, unstoppered cylinders with wide bases and horizontal graduations
Two graduated cylinders
the level of the liquid will be read at the bottom of the meniscus

Large graduated cylinders are usually made up of polypropylene for its excellent chemical resistance or polymethylpentene for its transparency, making them lighter and less fragile than glass. Polypropylene (PP) is easy to repeatedly autoclave; however, autoclaving in excess of about 121 °C (250 °F) (depending on the chemical formulation: typical commercial grade polypropylene melts in excess of 177 °C (351 °F)), can warp or damage polypropylene graduated cylinders, affecting accuracy.[1]

I H N traditional graduated cylinder (A in the image) is usually narrow and tall so as to increase the accuracy and precision of volume measurement; it has a plastic or glass bottom and a "spout" for easy pouring of the measured liquid. An additional version is wide and low.

Mixing cylinders (B in the picture) have ground glass joints instead of a spout, so they can be closed with a stopper or connect directly with other elements of a manifold.[2] With this kind of cylinder, the metered liquid does not pour directly, but is often removed using a cannula. A graduated cylinder is meant to be read with the surface of the liquid at eye level, where the center of the meniscus shows the measurement line. Typical capacities of graduated cylinders are from 10 ml to 1000 ml.

Common uses

Graduated cylinders are often used to measure the volume of a liquid. Graduated cylinders are generally more accurate and precise than laboratory flasks and beakers, but they should not be used to perform volumetric analysis;[3] volumetric glassware, such as a volumetric flask or volumetric pipette, should be used, as it is even more accurate and precise. Graduated cylinders are sometimes used to measure the volume of a solid indirectly by measuring the displacement of a liquid.

Reading

To be able to read volume measured by graduated cylinder, 3 significant digits were used. Also, in order to read the volume accurately, the observation must be at an eye level and read at the bottom of a meniscus of the liquid level.[4] Referred to the picture on the right side of the page, 100ml graduated cylinder was used to measure the liquid. It was found that 60ml volume of the liquid was measured.

Measurement

The main reason as to why the reading of the volume is done via miniscus is due the nature of the liquid in a closed surrounded space. By nature, liquid in the cylinder would be attracted to the wall around it through molecular forces. This forces the liquid to take up either convex or concave shape, depending highly on the type of the liquid in graduated cylinder. By reading the liquid at the bottom part of a concave or the top part of the convex liquid is equivalent to reading the liquid at its miniscus. [5] From the picture, the level of the liquid will be read at the bottom of the meniscus, which is the concave. The most accurate of the reading that could be done here is reduced down to 1 ml due to the given means of measurement on the cylinder. From this, the derived error would be one tenth of the least figure. For instance, if the reading is done and the value calculated is set to be 36.5 mL. The error, give or take 0.1 mL, must be included too. Therefore, the more precise value equates to 36.6 +/- 1; 36.4 or 36.6 mL. Therefore, there are 3 significant figures from the reading. [6]

60ml volume measured by graduated cylinder

References

  1. ↑ "Graduated Cylinders, Plastic - SPI Supplies". www.2spi.com. Retrieved 2015-06-14.
  2. ↑ http://www.elementalscientific.net/store/scripts/prodView.asp?idproduct=1239
  3. ↑ Pradyot Patnaik (2003). "Specifications for volumetric ware". Dean's Handbook of Analytical Chemistry, 2nd Edition. McGraw-Hill. ISBN 978-0071410601.
  4. ↑ "graduated cylinder" (PDF). ohlone.edu. Retrieved 2015-06-25.
  5. ↑ "Volume Measurements with a Graduated Cylinder" (PDF). Retrieved 2016-02-04.
  6. ↑ "Math Skills - Scientific Notation". www.chem.tamu.edu. Retrieved 2016-02-12.
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