The alcohol thermometer or spirit thermometer is an alternative to the

mercury-in-glass thermometer The mercury-in-glass or mercury thermometer was invented by physicist Daniel Gabriel Fahrenheit in Amsterdam (1714). It consists of a bulb containing mercury attached to a glass tube of narrow diameter; the volume of mercury in the tube is much ...

and has similar functions. Unlike the mercury-in-glass thermometer, the contents of an alcohol thermometer are less toxic and will evaporate quickly. The ethanol version is the most widely used due to the low cost and relatively low hazard posed by the liquid in case of breakage. An organic liquid is contained in a glass bulb which is connected to a

capillary A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the bod ...

of the same glass and the end is sealed with an expansion bulb. The space above the liquid is a mixture of nitrogen and the vapor of the liquid. For the working temperature range, the

meniscus Meniscus may refer to: *Meniscus (anatomy), crescent-shaped fibrocartilaginous structure that partly divides a joint cavity *Meniscus (liquid) The meniscus (plural: ''menisci'', from the Greek for "crescent") is the curve in the upper surface ...

or interface between the liquid is within the capillary. With increasing temperature, the volume of liquid expands and the meniscus moves up the capillary. The position of the meniscus shows the temperature against an inscribed scale. The liquid used can be pure

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) a ...

kerosene Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning "wax", and was regi ...

or isoamyl acetate, depending on manufacturer and working temperature range. Since these are

transparent Transparency, transparence or transparent most often refer to: * Transparency (optics), the physical property of allowing the transmission of light through a material They may also refer to: Literal uses * Transparency (photography), a still, ...

, the liquid is made more visible by the addition of a red or blue dye. One half of the glass containing the capillary is usually enamelled white or yellow to give a background for reading the scale. The range of usefulness of the thermometer is set by the boiling point of the liquid used. In the case of the ethanol-filled thermometer, the upper limit for measurement is 78 °C (172.4 °F), which makes it useful for measuring daytime, nighttime and body temperatures, although not for anything much hotter than these. Ethanol-filled thermometers are used in preference to mercury for meteorological measurements of minimum temperatures and can be used down to −70 °C (−94 °F).

British Standard British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under the a ...

692:1990 ''Specification for Meteorological Thermometers'' The physical limitation of the ability of a thermometer to measure low temperature is the freezing point of the liquid used. Ethanol freezes at -114.9 °C (-174.82 °F). If an alcohol thermometer utilizes a combination of ethanol, toluene, and pentane, its lower temperature range may be extended to measure temperatures down to as low as −200 °C (−328 °F). However, the measurement temperature range c. −200 °C to 78 °C, is highly dependent upon the type of alcohol used.

History

The alcohol thermometer was the earliest efficient, modern-style instrument of temperature measurement. As is the case with many early, important inventions, several people are credited with the invention. These include

Ferdinando II de' Medici, Grand Duke of Tuscany Ferdinando II de' Medici (14 July 1610 – 23 May 1670) was grand duke of Tuscany from 1621 to 1670. He was the eldest son of Cosimo II de' Medici and Maria Maddalena of Austria. He was remembered by his contemporaries as a man of culture ...

, who in 1654 made sealed tubes partly filled with alcohol or urine, with a bulb and stem, depending on the expansion of a liquid, and independent of air pressure. Other sources, including the Encyclopædia Britannica, credit German scientist

Daniel Gabriel Fahrenheit Daniel Gabriel Fahrenheit FRS (; ; 24 May 1686 – 16 September 1736) was a physicist, inventor, and scientific instrument maker. Born in Poland to a family of German extraction, he later moved to the Dutch Republic at age 15, where he spen ...

with inventing the alcohol thermometer in 1709. Fahrenheit was a skilled

glassblower Glassblowing is a glassforming technique that involves inflating molten glass into a bubble (or parison) with the aid of a blowpipe (or blow tube). A person who blows glass is called a ''glassblower'', ''glassmith'', or ''gaffer''. A '' lampworke ...

and his alcohol thermometer was the world's first reliable thermometer.Encyclopedia of World Biography "Gabriel Fahrenheit"
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References

{{DEFAULTSORT:Thermometers, Alcohol Thermometers Meteorological instrumentation and equipment 1709 in science fr:Thermomètre#Thermomètre à alcool