Hydrometer

Ahydrometerorlactometeris an instrument used for measuring density orrelative densityofliquidsbased on the concept ofbuoyancy.They are typicallycalibratedandgraduatedwith one or more scales such asspecific gravity.

A hydrometer usually consists of a sealed hollow glass tube with a wider bottom portion forbuoyancy,aballastsuch asleadormercuryfor stability, and a narrow stem with graduations for measuring. The liquid to test is poured into a tall container, often agraduated cylinder,and the hydrometer is gently lowered into the liquid until it floats freely. The point at which the surface of the liquid touches the stem of the hydrometer correlates to relative density. Hydrometers can contain any number of scales along the stem corresponding to properties correlating to the density.

Hydrometers are calibrated for different uses, such as a lactometer for measuring the density (creaminess) of milk, a saccharometer for measuring the density of sugar in a liquid, or an alcoholometer for measuring higher levels of alcohol inspirits.

The hydrometer makes use ofArchimedes' principle:a solid suspended in a fluid is buoyed by a force equal to the weight of the fluid displaced by the submerged part of the suspended solid. The lower the density of the fluid, the deeper a hydrometer of a given weight sinks; the stem is calibrated to give a numerical reading.

History

The hydrometer probably dates back to the Greek philosopherArchimedes(3rd century BC) who used its principles to find the density of various liquids.^[1]^[2]An early description of a hydrometer comes from a Latin poem, written in the 2nd century AD by Remnius, who compared the use of a hydrometer to the method offluid displacementused by Archimedes to determine the gold content ofHiero II'scrown.^[3]

Hypatia of Alexandria(b.c.350–370; d.415 CE), an important female Greek mathematician, is the first person traditionally associated with the hydrometer.^[3]In a letter,Synesius of Cyreneasks Hypatia, his teacher, to make a hydrometer for him:

The instrument in question is a cylindrical tube, which has the shape of a flute and is about the same size. It has notches in a perpendicular line, by means of which we are able to test the weight of the waters. A cone forms a lid at one of the extremities, closely fitted to the tube. The cone and the tube have one base only. This is called the baryllium. Whenever you place the tube in water, it remains erect. You can then count the notches at your ease, and in this way ascertain the weight of the water.^[4]

According to theEncyclopedia of the History of Arabic Science,it was used byAbū Rayhān al-Bīrūnīin the 11th century and described byAl-Khaziniin the 12th century.^[5]It was rediscovered in 1612 by Galileo and his circle of friends, and used in experiments especially at the Accademia del Cimento.^[6]It appeared again in the 1675 work of Robert Boyle (who coined the name"hydrometer"),^[3]with types devised byAntoine Baumé(theBaumé scale),William Nicholson,andJacques Alexandre César Charlesin the late 18th century,^[7]more or less contemporarily withBenjamin Sikes' discovery of the device by which the alcoholic content of a liquid can be automatically determined. The use of the Sikes device was made obligatory by British law in 1818.^[8]

Ranges

The hydrometer sinks deeper in low-density liquids such askerosene,gasoline,andalcohol,and less deep in high-density liquids such asbrine,milk,andacids.It is usual for hydrometers to be used with dense liquids to have the mark 1.000 (for water) near the top of the stem, and those for use with lighter liquids to have 1.000 near the bottom. In many industries a set of hydrometers is used (1.0–0.95, 0.95–.) to have instruments covering the range of specific gravities that may be encountered.

Scales

Modern hydrometers usually measurespecific gravitybut different scales were (and sometimes still are) used in certain industries. Examples include:

API gravity,universally used worldwide by the petroleum industry.
Baumé scale,formerly used in industrial chemistry andpharmacology
Brixscale, primarily used in fruit juice, wine making and the sugar industry
Oechsle scale,used for measuring the density ofgrape must
Plato scale,primarily used inbrewing
Twaddell scale,formerly used in the bleaching and dyeing industries^[9]

Specialized hydrometers

Specialized hydrometers are frequently named for their use: a lactometer, for example, is a hydrometer designed especially for use with dairy products. They are sometimes referred to by this specific name, sometimes as hydrometers.

Alcoholometer

An alcoholmeter is a hydrometer that indicates the alcoholic strength of liquids which are essentially a mixture of alcohol and water. It is also known as aproof and Tralles hydrometer(afterJohann Georg Tralles,but commonly misspelled astrailleandtralle). It measures the density of the fluid. Where no sugar or other dissolved substances are present, the specific gravity of a solution of ethanol in water can be directly correlated to the concentration of alcohol. Saccharometers for measuring sugar-water mixtures measure densities greater than water. Many have scales marked with volume percents of "potential alcohol", based on a pre-calculated specific gravity. A higher "potential alcohol" reading on this scale is caused by a greater specific gravity, assumed to be caused by the introduction of dissolved sugars or carbohydrate based material. A reading is taken before and after fermentation and approximate alcohol content is determined by subtracting the post fermentation reading from the pre-fermentation reading.^[10]

These were important instruments for determining tax, and specific maker's instruments could be specified.Bartholomew Sikeshad a monopoly in the UK andMary Dicasand her family enjoyed a similar monopoly in the US.^[11]

Lactometer

A lactometer is used to check purity of cow's milk. The specific gravity of milk does not give a conclusive indication of its composition since milk contains a variety of substances that are either heavier or lighter than water. Additional tests for fat content are necessary to determine overall composition. The instrument is graduated into a hundred parts. Milk is poured in and allowed to stand until the cream has formed, then the depth of the cream deposit in degrees determines the quality of the milk. If the milk sample is pure, the lactometer floats higher than if it is adulterated or impure.^[12]^[13]

Saccharometer

A saccharometer is a type of hydrometer used for determining the amount of sugar in a solution, invented byThomas Thomson.^[14]It is used primarily bywinemakersandbrewers,^[15]and it can also be used in makingsorbetsand ice-creams.^[16]The first brewers' saccharometer was constructed by Benjamin Martin (with distillation in mind), and initially used for brewing by James Baverstock Sr in 1770.^[17]Henry Thrale adopted its use and it was later popularized by John Richardson in 1784.^[18]

It consists of a large weighted glass bulb with a thin stem rising from the top with calibrated markings. The sugar level can be determined by reading the value where the surface of the liquid crosses the scale. The higher the sugar content, the denser the solution, and thus the higher the bulb will float.

Thermohydrometer

A thermohydrometer is a hydrometer that has athermometerenclosed in the float section. For measuring the density of petroleum products, such as fuel oils, the specimen is usually heated in a temperature jacket with a thermometer placed behind it since density is dependent on temperature. Light oils are placed in cooling jackets, typically at 15 °C. Very light oils with many volatile components are measured in a variable volume container using a floatingpistonsampling device to minimize light end losses.^[19]

Battery hydrometer

The state of charge of alead-acidbattery can be estimated from the density of thesulfuric acidsolution used aselectrolyte.A hydrometer calibrated to read specific gravity relative to water at 60 °F (16 °C) is a standard tool for servicingautomobile batteries.Tables are used to correct the reading to the standard temperature. Hydrometers are also used for maintenance of wet-cell nickel-cadmium batteries to ensure the electrolyte is of the proper strength for the application; for this battery chemistry the specific gravity of the electrolyte is not related to the state of charge of the battery.

A battery hydrometer with thermometer (thermohydrometer) measures the temperature-compensated specific gravity and electrolyte temperature.

Antifreeze tester

Another automotive use of hydrometers is testing the quality of theantifreezesolution used for engine cooling. The degree of freeze protection can be related to the density (and so concentration) of the antifreeze; different types of antifreeze have different relations between measured density and freezing point.

Acidometer

An acidometer, or acidimeter, is a hydrometer used to measure the specific gravity of anacid.^[20]

Barkometer

A barkometer is calibrated to test the strength of tanning liquors used in tanningleather.^[21]

Salinometer

A salinometer is a hydrometer used to measure the salt content of the feed water to a marine steam boiler.

Urinometer

Aurinometeris a medical hydrometer designed forurinalysis.As urine's specific gravity is dictated by its ratio of solutes (wastes) to water, a urinometer makes it possible to quickly assess a patient's overall level of hydration.

Gallery

An alcohol meter in a still
Lactometer
Battery condition indicator to measure the density of the electrolyte in a lead–acid battery, indicating the charge of the battery (~1985)
Antifreeze tester measures the density of engine coolant, indicating its freezing point.

Use in soil analysis

A hydrometer analysis is the process by which fine-grained soils,siltsandclays,are graded. Hydrometer analysis is performed if the grain sizes are too small forsieve analysis.The basis for this test isStoke's Lawfor falling spheres in a viscous fluid in which the terminal velocity of fall depends on the grain diameter and the densities of the grain in suspension and of the fluid. The grain diameter thus can be calculated from a knowledge of the distance and time of fall. The hydrometer also determines the specific gravity (or density) of the suspension, and this enables the fraction of particles of a certain equivalent particle diameter to be calculated.^[22]

References

^Hornsey, Ian S. (2003).A history of beer and brewing.Cambridge: Royal Society of Chemistry. p. 429.ISBN 978-0-85404-630-0.
^Bendick, Jeanne (2011) [1962].Archimedes And The Door Of Science.Literary Licensing, LLC. pp. 63–64.ISBN 9781258014889.
^^a ^b ^cBensaude-Vincent, Bernadette(2000).Holmes, Frederic L.;Levere, Trevor H.(eds.).Instruments and Experimentation in the History of Chemistry.Massachusetts Institute of Technology Press. p. 153.ISBN 9780262082822.
^FitzGerald, Augustine (1926)."Letter 15 - To the Philosopher (Hypatia)".The Letters of Synesius of Cyrene.Oxford University Press. p. 99.hdl:2027/mdp.39015008616180.
^Rozhanskaya, Mariam; Levinova, I. S. (1996)."Statics".In Rushdī Rāshid; Régis Morelon (eds.).Encyclopedia of the History of Arabic Science, Volume 2.Routledge.pp. 614–642 [639].ISBN 978-0-415-12411-9.Retrieved2019-03-26.
^"In-depth Hydrometer".Museo Galileo.Retrieved2024-01-01.
^Blondel, Claude-Joseph (2003)."Un enfant illustre de Beaugency: le physicien et aéronaute Jacques Charles (1746-1823)"[An illustrious child of Beaugency: the physicist and aeronaut].Les Publications de l'Académie d'Orléans, Agriculture, Sciences, Belles-lettres et Arts(in French) (4). Académie d'Orléans: 37.
^Denison, Merrill (1955).The Barley and the Stream: The Molson Story.Toronto: McClelland & Stewart. p. 132.
^Dick, William Brisbane (1975)."Degrees of Baum'e".Dick's Encyclopedia of Practical Receipts and Processes.New York: Dick and Fitzgerald, Publishers.ISBN 9780308101579.
^Rabin, Dan; Forget, Carl (1998).The dictionary of beer and brewing.London: Fitzroy Dearborn.ISBN 9781579580780.Retrieved2009-10-11.
^Morrison-Low, A. D. (2004-09-23)."Dicas [married name Arstall], Mary (fl. 1800–1815), maker of scientific instruments".Oxford Dictionary of National Biography.Vol. 1 (online ed.). Oxford University Press.doi:10.1093/ref:odnb/49542.ISBN 978-0-19-861412-8.(Subscription orUK public library membershiprequired.)
^Geisler, Joseph F. (1891)."Signification of Lactometer Tests".Journal of the American Chemical Society.13(2): 93–98.doi:10.1021/ja02124a009.ISSN 0002-7863.
^"Glass lactometer, England, 1875-1900".Science Museum Group Collection.Retrieved2024-01-01.
^Thomson, Thomas (1840).Explanation of Allan's Saccharometer: Appointed by Act of Parliament for the Use of Distillers, & C.D. & W. Millar.
^Sambrook, Pamela (1996).Country House Brewing in England, 1500-1900.A&C Black.ISBN 9781852851279.Retrieved2009-10-11.
^Hanneman, Leonard J. (1993).Patisserie.Butterworth-Heinemann.ISBN 9780750604307.Retrieved2009-10-11.
^Mathias, Peter (1959).The Brewing Industry in England 1700-1830.University Press.Retrieved2012-03-16.
^Bud, Robert; Warner, Deborah Jean; Chaplin, Simon; Johnston, Stephen; Peterson, Betsy Bahr (1998).Instruments of Science: An Historical Encyclopedia.Science Museum, London, and National Museum of American History, Smithsonian Institution.ISBN 9780815315612.Retrieved2009-10-11.
^Béla G. Lipták; Kriszta Venczel, eds. (2017).Instrument and automation engineers' handbook: measurement and safety(Fifth ed.). United States: Taylor & Francis Group, CRC Press. p. 1314.ISBN 978-1-4987-2764-8.
^"Acidometer".The Free Dictionary.Farlex. 2003.Retrieved18 September2010.
^Davis, Charles Thomas (1897).The manufacture of leather: being a description of all of the processes for the tanning and tawing with bark, extracts, chrome and all modern tannages in general use.H. C. Baird & co.Retrieved2009-10-11.Barkometer.
^Fakhry A. Assaad, Philip Elmer LaMoreaux, Travis H. Hughes (ed.),Field Methods for Geologists and Hydrogeologists,Springer Science & Business Media, 2004ISBN 3540408827,p.299

Sources

Hypatia of Alexandria
Hydrometer Information
Guide to Brewing Hydrometers
Jurjen Draaijer.Milk Testing Archived2012-10-21 at theWayback Machine.Milk Producer Group Resource Book,Food and Agriculture Organization of the United Nations
Using Your Hydrometer,Winemaking Home Page.
How The Hydrometer Works,Home Winemaking Techniques

[1] Hornsey, Ian S. (2003).A history of beer and brewing.Cambridge: Royal Society of Chemistry. p. 429.ISBN 978-0-85404-630-0.

[2] Bendick, Jeanne (2011) [1962].Archimedes And The Door Of Science.Literary Licensing, LLC. pp. 63–64.ISBN 9781258014889.

[bensaude-vincent-3] Bensaude-Vincent, Bernadette(2000).Holmes, Frederic L.;Levere, Trevor H.(eds.).Instruments and Experimentation in the History of Chemistry.Massachusetts Institute of Technology Press. p. 153.ISBN 9780262082822.

[4] FitzGerald, Augustine (1926)."Letter 15 - To the Philosopher (Hypatia)".The Letters of Synesius of Cyrene.Oxford University Press. p. 99.hdl:2027/mdp.39015008616180.

[5] Rozhanskaya, Mariam; Levinova, I. S. (1996)."Statics".In Rushdī Rāshid; Régis Morelon (eds.).Encyclopedia of the History of Arabic Science, Volume 2.Routledge.pp. 614–642 [639].ISBN 978-0-415-12411-9.Retrieved2019-03-26.

[6] "In-depth Hydrometer".Museo Galileo.Retrieved2024-01-01.

[7] Blondel, Claude-Joseph (2003)."Un enfant illustre de Beaugency: le physicien et aéronaute Jacques Charles (1746-1823)"[An illustrious child of Beaugency: the physicist and aeronaut].Les Publications de l'Académie d'Orléans, Agriculture, Sciences, Belles-lettres et Arts(in French) (4). Académie d'Orléans: 37.

[8] Denison, Merrill (1955).The Barley and the Stream: The Molson Story.Toronto: McClelland & Stewart. p. 132.

[9] Dick, William Brisbane (1975)."Degrees of Baum'e".Dick's Encyclopedia of Practical Receipts and Processes.New York: Dick and Fitzgerald, Publishers.ISBN 9780308101579.

[10] Rabin, Dan; Forget, Carl (1998).The dictionary of beer and brewing.London: Fitzroy Dearborn.ISBN 9781579580780.Retrieved2009-10-11.

[11] Morrison-Low, A. D. (2004-09-23)."Dicas [married name Arstall], Mary (fl. 1800–1815), maker of scientific instruments".Oxford Dictionary of National Biography.Vol. 1 (online ed.). Oxford University Press.doi:10.1093/ref:odnb/49542.ISBN 978-0-19-861412-8.(Subscription orUK public library membershiprequired.)

[12] Geisler, Joseph F. (1891)."Signification of Lactometer Tests".Journal of the American Chemical Society.13(2): 93–98.doi:10.1021/ja02124a009.ISSN 0002-7863.

[13] "Glass lactometer, England, 1875-1900".Science Museum Group Collection.Retrieved2024-01-01.

[14] Thomson, Thomas (1840).Explanation of Allan's Saccharometer: Appointed by Act of Parliament for the Use of Distillers, & C.D. & W. Millar.

[15] Sambrook, Pamela (1996).Country House Brewing in England, 1500-1900.A&C Black.ISBN 9781852851279.Retrieved2009-10-11.

[16] Hanneman, Leonard J. (1993).Patisserie.Butterworth-Heinemann.ISBN 9780750604307.Retrieved2009-10-11.

[17] Mathias, Peter (1959).The Brewing Industry in England 1700-1830.University Press.Retrieved2012-03-16.

[18] Bud, Robert; Warner, Deborah Jean; Chaplin, Simon; Johnston, Stephen; Peterson, Betsy Bahr (1998).Instruments of Science: An Historical Encyclopedia.Science Museum, London, and National Museum of American History, Smithsonian Institution.ISBN 9780815315612.Retrieved2009-10-11.

[19] Béla G. Lipták; Kriszta Venczel, eds. (2017).Instrument and automation engineers' handbook: measurement and safety(Fifth ed.). United States: Taylor & Francis Group, CRC Press. p. 1314.ISBN 978-1-4987-2764-8.

[20] "Acidometer".The Free Dictionary.Farlex. 2003.Retrieved18 September2010.

[21] Davis, Charles Thomas (1897).The manufacture of leather: being a description of all of the processes for the tanning and tawing with bark, extracts, chrome and all modern tannages in general use.H. C. Baird & co.Retrieved2009-10-11.Barkometer.

[22] Fakhry A. Assaad, Philip Elmer LaMoreaux, Travis H. Hughes (ed.),Field Methods for Geologists and Hydrogeologists,Springer Science & Business Media, 2004ISBN 3540408827,p.299

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