Laboratory burette

November 1, 2021

In the laboratory, burettes are necessary and essential instruments to accurately measure volumes of liquids that are at a certain temperature. They are high-precision instruments, so the steps for their use are specific and must be followed to the letter to avoid errors.

What is it?

It is an elongated, graduated container with a tubular shape and a uniform internal diameter. Its main use is volumetric, since in laboratories it is required to accurately measure volumes of liquids that are at certain temperatures.

An example of the volumetric use of a burette is the titration of acid-base solutions. With a buret it is possible to know with total accuracy, the amount of base that is needed to neutralize an acid or vice versa, allowing to calculate its concentration.

Types of burettes

There are two main types of burettes:

Geissler burettes: It has a ground glass key. Avoid keeping the liquid in contact with the burette for a long time, as it can clog the tap.

Mohr’s burette : In this type of buret, the key is replaced by a rubber tube with a glass ball inside. This mechanism acts like a valve. Allows you to pour liquids drop by drop.

Causes of burette errors

Lubricant on the burette keys: It is not necessary to apply lubricant to ensure a good seal.

Drops sticking to the bottom: A drop can be up to 0.05 ml, an amount that can be a very large error in small-scale studies. If a drop remains on the tip of the burette, it is convenient to collect it with the container that is receiving the substance, to do this simply touch the drop with one of the walls of the flask or Erlenmeyer flask.

Tiny air bubbles adhering to the faucet: May alter the measurement.

Quick emptying: Traces of liquid may remain on the walls of the burette.

Dust contamination: The top of the burette must be protected.

How is it used?

  1. Keep the burette upright by attaching it to the universal holder.
  2. The burette should be rinsed with the liquid that will fill it to remove bubbles and adequately cover the walls to avoid mistakes.
  3. Fill the burette above the 0.00 mL mark using a graduated pipette or funnel.
  4. Open the clamp that seals the burette to allow the burette to fill.
  5. Evaluate that there are no air bubbles. If this happens you should cover the exit hole of the spout with a finger, remove the clamp and press the rubber to eliminate the bubbles. If necessary, fill the burette again.
  6. Dry the outside of the burette spout.
  7. Rest the spout on a clean and dry wall of the container that you will use to dispose of liquids. Open the clamp until the liquid level reaches 0.00 ml. For this, the base of the meniscus must be tangent to the line that marks 0.00 ml.
  8. During the titration process, you must handle the buret tap with care. For this task you will use your non-skilled hand. The hand should go around the burette and the fingers should apply the necessary pressure on the clamp or key. The skilled hand is free to shake the titration flask.
Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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