Burette

A burette is a volumetric measuring glassware which is used in analytical chemistry for the accurate dispensing of a liquid, especially of one of the reagents in a titration.{{Cite web|url=http://www.chem.yorku.ca/profs/hempsted/chemed/equipment/burette.html|title=Burettes|website=chem.yorku.ca}} The burette tube carries graduated marks from which the dispensed volume of the liquid can be determined.{{Cite news|url=http://www.gcsescience.com/aa30.htm|title=Acids and Alkalis|work=gcsescience}} Compared to a volumetric pipette, a burette has similar precision if used to its full capacity, but as it is usually used to deliver less than its full capacity, a burette is slightly less precise than a pipette.{{Cite web|url=http://www.titrations.info/pipette-burette|title=Laboratory volumetric glassware used in titration - burette, pipette, ASTM E287-02 standard specification|website=www.titrations.info|language=en|access-date=2018-12-31}}

The burette is used to measure the volume of a dispensed substance, but is different from a graduated cylinder as its graduations measure from top to bottom. Therefore, the difference between the starting and the final volume is equal to the amount dispensed.{{Cite web|url=http://www.preproom.org/equipment/eq.aspx?eqID=5107&favourite=0|title=Burette - Preproom.org|access-date=2017-05-23}} The precision and control of the burette over other means of adding solution is beneficial for use in titration.

A volumetric burette can be made of glass or plastic, and is a straight tube with a graduation scale. At the tip of burette, there are a stopcock and valve to control the flow of the chemical solution. The barrel of the stopcock can 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 for specific tolerances, designated as class A or B and this also is etched on the glass.

File:Black_strip_2.jpg

In order to measure the amount of solution added in or drained out, the burette must be observed at eye level straight to the bottom of the meniscus. The liquid in the burette should be completely free of bubbles to ensure accurate measurements.{{Cite book|title=A laboratory for General, Organic & Biochemistry|last1=Henrickson|first1=Charles H.|last2=Byrd|first2=Larry C.|last3=Hunter|first3=Norman W.|publisher=The Mcgraw-Hill Companies, Inc|year=2000|chapter=1}} The difference in volume can be calculated by taking the difference of the final and initial recorded volume.{{Cite book|title=Experimental Chemistry|last1=Sienko|first1=Michell J.|last2=Plane|first2=Robert A.|last3=Marcus|first3=Stanley T.|publisher=McGraw-Hill. Inc|year=1984|pages=16}} Using the burette with a colorless solution may make it difficult to observe the bottom of the meniscus, so the black strip technique{{Cite web |last=Seely |first=Oliver |title=Helpful Hints on the Use of a Burette |url=http://www2.csudh.edu/oliver/demos/buretuse/buretuse.htm |access-date=2022-06-01 |website=www2.csudh.edu}} can make it easier to accurately observe and record measurements.

The specification of a volumetric burette indicates its properties, such as the nominal volume, volume unit, error limit, and accuracy class, plus other related details from the manufacturer.{{Cite web|url=http://limshelp.labware.com/limsv6/V6Help_MAIN.htm?turl=WordDocuments/121specificationsconcepts.htm|title=LabWare LIMS v6 Help|website=limshelp.labware.com|access-date=2017-06-20}} The nominal volume and error limit is usually given in units of mL or cm³. Another specification commonly found on burettes is the calibration mark "TD" or "Ex". This stands for "calibrated to deliver", indicating that the printed volume is accurate when the burette is used to deliver (rather than contain) a solution.{{Cite web|url=http://www.harpercollege.edu/tm-ps/chm/100/dgodambe/thedisk/labtech/volume.htm|title=Measuring Volume|website=www.harpercollege.edu|access-date=2017-06-20|archive-date=2017-07-04|archive-url=https://web.archive.org/web/20170704203554/http://www.harpercollege.edu/tm-ps/chm/100/dgodambe/thedisk/labtech/volume.htm|url-status=dead}} Another commonly indicated specification is the accuracy class, including class A and class B. Class A is preferred to Class B when volumetric accuracy is important, as it has a narrower range of error with accuracy up to 0.1 percent compared to 0.2 percent in Class B burette.{{Cite web|url=http://www.jaytecglass.co.uk/laboratory-glassware/general-volumetric-glassware/burette/|title=Burette – Jaytec Glass|website=www.jaytecglass.co.uk|language=en-US|access-date=2017-06-20|archive-date=2018-01-20|archive-url=https://web.archive.org/web/20180120070126/https://www.jaytecglass.co.uk/laboratory-glassware/general-volumetric-glassware/burette/|url-status=dead}}{{Cite web |title=Volumetric Measurement in the Laboratory |url=https://www.labunlimited.co.uk/CAR1/CAR1-LAB/pdf/BRAND_Volumetric%20Measurement.pdf}}

File:Specification of burette.jpg

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 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 a computer; for example, a titration may be recorded digitally and then subject to numerical processing to find the titer at an end-point.

The first burette was invented in 1845 by the French chemist Étienne-Ossian Henry (1798–1873).{{cite journal|last1=Henry|first1=O.|title=Nouvelles expériences sur l'essai des potasses du commerce et appareil dit potassimètre pour l'effectuer|journal=Journale de Pharmacie et de Chimie|date=1845|volume=7|pages=214–222|url=https://babel.hathitrust.org/cgi/pt?id=hvd.hx3kbt;view=1up;seq=216|series=3rd series|trans-title=New experiments on the assay of commercial potash and an apparatus called a "potassimeter" to perform it|language=fr}} A sketch of Henry's burette appears on p. 218. From p. 218: "AC est un tube de verre d'une longuere de 60 centimètres environ, et d'un diamètre de 4 millimètres à peu près. En A se trouve un entonnoir de verre soudé ou adapté à volunté; et en B un petite robinet en cuivre terminé par un tube capillaire. Ce robinet s'adjuste au tube par un bon bouchon et avec de la cire à cacheter. Le tube AB est fixé par deux crochets au long d'une échelle inscrite sur une planche, et cette échelle est divisé en 100 parties égales. Le tout est supporté par un pied qui permet de placer le tube AB au-dessus du vase M contenant le sel de potasse à essayer." (AC is a glass tube [that's] about 60 cm. long, and nearly 4 mm. in diameter. At A, a glass funnel is joined or fitted as desired; and at B [there is] a small copper valve ending with a capillary tube. This valve is fitted to the tube by a good cap and with sealing wax. The tube AB is fixed by two brackets along a scale [that's] inscribed on a plate, and this scale is divided into 100 equal parts. The whole is supported by a base that permits placing the tube AB above a vase M containing the potassium salt to be assayed.)See:

• {{cite journal|last1=Szabadváry|first1=Ferenc|title=The history of chemical laboratory equipment|journal=Periodica Polytechnica Chemical Engineering|date=1986|volume=30|issue=1–2|pages=77–95|url=https://pp.bme.hu/ch/article/view/2829/1934}} See p. 87.
• {{cite book|last1=Szabadváry|first1=Ferenc|title=History of Analytical Chemistry|date=1966|publisher=Permagon Press|location=Oxford, England|page=237|isbn=9781483157122|url=https://books.google.com/books?id=icn9BAAAQBAJ&pg=PA237|translator=Gyula Svehla}}
• {{cite journal|last1=Christophe|first1=R.|title=L'analyse volumétrique de 1790 à 1860. Caractéristiques et importance industrielle. Evolution des instruments.|journal=Revue d'histoire des sciences|date=1971|volume=24|issue=1|pages=25–44|doi=10.3406/rhs.1971.3172|url=http://www.persee.fr/doc/rhs_0151-4105_1971_num_24_1_3172|trans-title=Volumetric analysis from 1790–1860. Characteristics and industrial importance. Evolution of instruments.|language=fr}} From p. 38: " … il préfigure bien ses descendants actuelles … " ( … it [i.e., Henry's burette] foreshadows well its modern descendants … ) In 1855, the German chemist Karl Friedrich Mohr (1806–1879) presented an improved version of Henry's burette, having graduations inscribed on the tube of the burette.{{cite book|last1=Mohr|first1=Karl Friedrich|title=Lehrbuch der chemisch-analytischen Titrirmethode … , part 1|date=1855|publisher=Friederich Vieweg und Sohn|location=Braunschweig, (Germany)|pages=2–20|url=https://babel.hathitrust.org/cgi/pt?id=wu.89087461158;view=1up;seq=22|trans-title=Textbook of analytical chemistry titration methods … |language=de}} Page 3 shows Mohr's burette; page 12 shows a burette with a glass stopcock (Glasshahn).

The word "burette" was coined in 1824 by the French chemist Joseph Louis Gay-Lussac (1778–1850).{{cite journal|last1=Gay-Lussac|first1=Joseph Louis|title=Instruction sur l'essai du chlorure de chaux|journal=Annales de chimie et de physique|date=1824|volume=26|pages=162–175|url=https://babel.hathitrust.org/cgi/pt?id=hvd.hx3dwa;view=1up;seq=181|series=2nd series|trans-title=Instructions on the assaying of chlorinated lime|language=fr}} On p. 171, Gay-Lussac describes various figures that appear in a plate (illustration) that accompanies the article. From p. 171: " I, burette destinée à mesurer la teinture d'épreuve: … " (I, burette intended to measure the test dye: … )

File:Meniscus of water in burette.JPG|Meniscus

File:Buret.png

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File:Burette stand and burette .jpg|Burette with ring stand

File:Stopcock .jpg|alt=plastic stopcock used in glass volumetric burette|Plastic stopcock used in glass volumetric burette

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• [https://web.archive.org/web/20041024082522/http://www.dartmouth.edu/~chemlab/techniques/buret.html Using a Burette] from ChemLab at Dartmouth College demonstrating how to use a burette correctly
• [http://chemed.chem.purdue.edu/genchem/lab/equipment/buret/use.html Use of the Buret]

{{Laboratory equipment|Glass}}

Category:Laboratory equipment

Category:Volumetric instruments

Category:French inventions