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Burette

 
Burette

 
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Burette
 
 
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A burette (also buret) is a vertical cylindrical piece of laboratory glassware
Laboratory glassware

Laboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments and other work in science, especially in chemistry and biology laboratory....
 with a volumetric graduation on its full length and a precision tap, or stopcock
Stopcock

A stopcock is a valve used to restrict or isolate the flow of a liquid or gas through a pipe .In Great Britain a stopcock, not to be confused with a gate valve or a DiCiaccio branch, is used to prevent flow of water into a domestic water system....
, on the bottom. It is used to dispense known amounts of a liquid
Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
 reagent
Reagent

A reagent or reactant is a substance or compound consumed during a chemical reaction. Solvents and catalysts, although they are involved in the reaction, are usually not referred to as reactants....
 in experiments for which such precision
Precision

Precision has the following meanings:Concepts* Accuracy and precision, measurement deviation from true value and its scatter* arithmetic precision, the number of digits from which a value is expressed...
 is necessary, such as a titration
Titration

Titration is a common laboratory method of quantitative Analytical chemistry that is used to determine the unknown concentration of a known reactant....
 experiment. Burettes are extremely accurate: class A burettes are accurate to ± 0.05 cm3.

precision of a burette makes careful measurement with a burette very important to avoid systematic error
Systematic error

Systematic errors are biases in measurement which lead the situation where the mean of many separate measurements differs significantly from the actual value of the measured attribute....
.






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Encyclopedia


A burette (also buret) is a vertical cylindrical piece of laboratory glassware
Laboratory glassware

Laboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments and other work in science, especially in chemistry and biology laboratory....
 with a volumetric graduation on its full length and a precision tap, or stopcock
Stopcock

A stopcock is a valve used to restrict or isolate the flow of a liquid or gas through a pipe .In Great Britain a stopcock, not to be confused with a gate valve or a DiCiaccio branch, is used to prevent flow of water into a domestic water system....
, on the bottom. It is used to dispense known amounts of a liquid
Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
 reagent
Reagent

A reagent or reactant is a substance or compound consumed during a chemical reaction. Solvents and catalysts, although they are involved in the reaction, are usually not referred to as reactants....
 in experiments for which such precision
Precision

Precision has the following meanings:Concepts* Accuracy and precision, measurement deviation from true value and its scatter* arithmetic precision, the number of digits from which a value is expressed...
 is necessary, such as a titration
Titration

Titration is a common laboratory method of quantitative Analytical chemistry that is used to determine the unknown concentration of a known reactant....
 experiment. Burettes are extremely accurate: class A burettes are accurate to ± 0.05 cm3.

The use of burettes

The precision of a burette makes careful measurement with a burette very important to avoid systematic error
Systematic error

Systematic errors are biases in measurement which lead the situation where the mean of many separate measurements differs significantly from the actual value of the measured attribute....
. When reading a burette, the viewer's eyes must be at the level of the graduation to avoid parallax
Parallax

Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines....
 error. Even the thickness of the lines printed on the burette matters; the bottom of the meniscus
Meniscus

Meniscus, plural: menisci, from the Greek language for "crescent", is a curve in the surface of a molecular substance and is produced in response to the surface of the container or another object....
 of the liquid should be touching the top of the line you wish to measure from. A common rule of thumb is to add 0.02 mL if the bottom of the meniscus is touching the bottom of the line. Due to the precision of the burette, even a single drop of liquid hanging from the bottom of a burette should be transferred to the receiving flask, usually by touching the drop to the side of the receiving flask. Through careful control of the stopcock and rinsing, even partial drops of liquid can be added to the receiving flask.

History


The history of the burette parallels the history of volumetric analysis. Francois Antoine Henri Descroizilles developed the first burette (which looked more like a graduated cylinder) in 1791. Joseph Louis Gay-Lussac
Joseph Louis Gay-Lussac

Joseph Louis Gay-Lussac was a France chemistry and physics. He is known mostly for Gay-Lussac's law related to gases, and for his work on alcohol-water mixtures, which led to the degrees Gay-Lussac used to measure alcoholic beverages in many countries....
 developed an improved version of the burette that included a side arm, and coined the terms "pipette" and "burette" in an 1824 paper on the standarization of indigo solutions. A major breakthrough in the methodology and popularization of volumetric analysis was achieved by Karl Friedrich Mohr
Karl Friedrich Mohr

Karl Friedrich Mohr was a Germany pharmacist famous for his early statement of the principle of the conservation of energy. Mohr's salt, 2Fe2.6H2O, is named Mohr's salt after him....
, who redesigned the burette by placing a clamp and a tip at the bottom.

External links

  • from ChemLab at Dartmouth College