A burette (also buret) is a laboratory equipment used in analytical chemistry for the dispensing of variable, measured amounts of a chemical solution. A volumetric burette delivers measured volumes of liquid. Piston burettes are similar to syringes, but with precision bore and plunger. Piston burettes may be manually operated or may be motorized.[1] A weight burette delivers measured weights of liquid.[2]
Overview
editA burette a volumetric measuring glassware which used in analytical chemistry for accurate dispensing of variable, measured the volume of a liquid, especially of one of the reagents in a titration.[3]
- Purpose: Burette used to measured in volume in the specific amount but different from measuring cylinder as its graduations measure from top to bottom. Therefore the difference between the starting and final volume is equal to the amount dispensed.[4] The precise measureing of Burette is beneficial to used in titration in order to add titrant to the titrated solution [5]
Types
editThere are two main types of Burette which manual Burette and Digital Burette
Volumetric Burette
edit
A volumetric burette consists of glass tube of constant bore with a graduation scale etched on it and a stopcock at the bottom. The barrel of the stopcock may be made of glass or the plastic PTFE. Stopcocks with glass barrels need to be lubricated with vaseline or a specialized grease. Burettes are manufactured to specified tolerances, designated as class A or B and this also is etched on the glass.
- Reading the Burette The amount of solution added in or drained out need to be read correctly by observed at the eye level straight to the bottom of "Menicus"
Reading the data at the eye level means looking straight ahead at the bottom of meniscus
- Techniques to read the Burette
Using the burette with colorless solution is sometime difficult to observe the bottom of the meniscus so Black Strip Technique[6] can help to accurately observe and measure the number on the scale. Moreover, the number should be report in two decimal places number which can be easier done by using Black strip Technique. The black stripped can be written with pen on the normal white paper or it can be printed it out. However, it is necessary to use the white color paper as the background so the scale is still readable.
- Specification on Burette
The specification of burette is on the topmost of it (not the side with stopcock). Specification is used to select the appropriate burette according to the purpose of usage. Example of specification are Nominal volume, volume unit, Accuracy classification, Delivery and waiting time. (add photo)
- Accuracy classification is at the top of the burette along with other specification.There are only two classes based on the level of accuracy which are Class A/AS and Class B.
For Class A burette,
Specification
editSpecification or product specification are used as a identification of volumetric burette[7] for example nominal volume, volume unit, error limit, class of the burette and other manufacture's related details. It is necessary to be able to identify the difference in burette specification in order to perform the accurate experiment since the usage of burette is associated with its specification. Nominal volume, error and units are the basic knowledge in order to distinguish the delivery volume of the certain solution from the burette. Another specification for burette is called calibration marked as TD or Ex stand for "Calibration to Deliver". it used to indicate that this burette is butter used to delivery purpose which the amount will be correspond to the volume as specified[8] The accuracy classes also shown in specification of burette as well and it includes class A and class B. Class A will be used when volumetric accuracy is important for the accuracy of the experiment with accuracy up to 0.1 percent[9].
| Burette accuracy /mL | ||
|---|---|---|
| Capacity, mL | Class A | Class B |
| 10 | 0.02 | 0.04 |
| 25 | 0.03 | 0.06 |
| 50 | 0.05 | 0.10 |
| 100 | 0.10 | 0.20 |
Digital Burette or Piston Burette
editTitration curve (blue) for malonic acid and 2nd. derivative (green). The part in the light blue box is magnified 10 times
Digital burettes are based on a syringe design. The barrel and plunger may be made of glass. With liquids that corrode glass, including solutions of alkali, the barrel and plunger may be made of polyethylene or another resistant plastic material. The barrel is held in a fixed position and the plunger is moved incrementally either by turning a ratcheted wheel by hand, or by means of a step-motor. The volume is shown on a digital display. A high-precision syringe may be used to deliver very precise aliquots. Motorized digital burettes may be controlled by computer; for example, a titration may be recorded digitally and then subject to numerical processing to find the titre at an end-point.
- ^ Mendham, J.; Denney, R. C.; Barnes, J. D.; Thomas, M. J. K. (2000), Vogel's Quantitative Chemical Analysis (6th ed.), New York: Prentice Hall, ISBN 0-582-22628-7 Section 3.12, p.79, "Burettes"
- ^ Redman, H. N. (1963). "An improved type of weight burette for use in volumetric analysis". Analyst. 88 (1049): 654–655. doi:10.1039/AN9638800654.
- ^ Chauhan, Yogesh. "Burettes, Laboratory Glassware" (Document).
{{cite document}}: Cite document requires|publisher=(help); Cite has empty unknown parameter:|url=(help); Unknown parameter|website=ignored (help) - ^ "Burette - Preproom.org". Retrieved 2017-05-23.
- ^ "Laboratory volumetric glassware used in titration - burette, pipette, ASTM E287-02 standard specification". www.titrations.info. Retrieved 2017-05-23.
- ^ Seely, Oliver. "Helpful Hints on the Use of a Buret". www.csudh.edu. Retrieved 2017-06-09.
- ^ "LabWare LIMS v6 Help". limshelp.labware.com. Retrieved 2017-06-20.
- ^ "Measuring Volume". www.harpercollege.edu. Retrieved 2017-06-20.
- ^ "Burette – Jaytec Glass". www.jaytecglass.co.uk. Retrieved 2017-06-20.