A eudiometer is a laboratory device that measures the change in

volume Volume is a measure of regions in three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch) ...

of a

gas Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...

mixture following a physical or

chemical A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combin ...

change.

Description

Depending on the reaction being measured, the device can take a variety of forms. In general, it is similar to a

graduated cylinder A graduated cylinder, also known as a measuring cylinder or mixing cylinder, is a common piece of laboratory equipment used to measure the volume of a liquid. It has a narrow cylindrical shape. Each marked line on the graduated cylinder represent ...

, and is most commonly found in two sizes: 50 mL and 100 mL. It is closed at the top end with the bottom end immersed in

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

or mercury. The liquid traps a sample of gas in the cylinder, and the graduation allows the volume of the gas to be measured. For some reactions, two

platinum Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...

wires (chosen for their non-reactivity) are placed in the sealed end so an

electric spark An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an Ionization, ionized, Electric current, electrically conductive channel through a normally-insulating medium, often air or other ga ...

can be created between them. The electric spark can initiate a reaction in the gas mixture and the graduation on the cylinder can be read to determine the change in volume resulting from the reaction. The use of the device is quite similar to the original

barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...

, except that the gas inside displaces some of the liquid that is used.

History

In 1772,

Joseph Priestley Joseph Priestley (; 24 March 1733 – 6 February 1804) was an English chemist, Unitarian, Natural philosophy, natural philosopher, English Separatist, separatist theologian, Linguist, grammarian, multi-subject educator and Classical libera ...

began experimenting with different "airs" using his own redesigned

pneumatic trough A pneumatic trough is a piece of laboratory apparatus used for collecting gases, such as hydrogen, oxygen and nitrogen. It is mainly made of glass or various fibres and are of various sizes. It was invented by Stephen Hales. Description Four i ...

in which mercury instead of water would trap gases that were usually soluble in water. From these experiments Priestley is credited with discovering many new gases such as

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

hydrogen chloride The Chemical compound, compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hyd ...

, and

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

. He also discovered a way to find the purity or "goodness" of air using "nitrous air test". The eudiometer functions on the greater

solubility In chemistry, solubility is the ability of a chemical substance, substance, the solute, to form a solution (chemistry), solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form su ...

of NO₂ in water over NO, and the oxidation reaction of NO into NO₂ by air oxygen: : 2 NO + O₂ → 2 NO₂. A quantity of air is combined with NO over water, and the more soluble compound NO₂ dissolves, leaving the remaining air somewhat contracted in volume. The richer the air was in oxygen, the greater was the contraction.Geerdt Magiels (2009) ''From Sunlight to Insight. Jan IngenHousz, the discovery of photosynthesis & science in the light of ecology'', Chapter 5: A crucial instrument: the rise and fall of the eudiometer, pages=199-231, VUB Press Marsilio Landriani was studying pneumatic chemistry with Pietro Moscati when they attempted to quantify Priestley's nitric acid test for air quality. Landriani used a pneumatic trough in the form of a tall, graduated cylinder over water. As it measured the salubrity of air, he called it a eudiometer"Eudiometer". IMSS
from

Museo Galileo Museo Galileo (formerly ''Istituto e Museo di Storia della Scienza''; Institute and Museum of the History of Science) is located in Florence, Italy, in Piazza dei Giudici, along the River Arno and close to the Uffizi Gallery. The museum, dedicat ...

An associate of Moscati's, Felice Fontana also designed a eudiometer on the same principles and quantified the salubrity of the air. The eudiometer with the nitrous air test was the way

Jan Ingenhousz Jan Ingenhousz FRS (8 December 1730 – 7 September 1799) was a Dutch-British physiologist, biologist and chemist. He is best known for discovering photosynthesis by showing that light is essential to the process by which green plants absorb ...

verified that the bubbles given off under water by plant leaves exposed to sunlight were oxygen bubbles. His description of

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

was published in 1779, and in 1785 he wrote about eudiometers in '' Journal de Physique'' (v 26, p 339). According to a biographer, Ingenhousz indicated that "many instruments were called eudiometers although strictly speaking they didn't deserve the name ... misunderstandings could exist when not everybody was using the same instruments." An electrified version of the eudiometer was developed by Count

Alessandro Volta Alessandro Giuseppe Antonio Anastasio Volta (, ; ; 18 February 1745 – 5 March 1827) was an Italian chemist and physicist who was a pioneer of electricity and Power (physics), power, and is credited as the inventor of the electric battery a ...

(1745–1827), an Italian physicist who is well known for his contributions to the

electric battery An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections for powering electrical devices. When a battery is supplying power, its positive Terminal (electronics), terminal is the ...

and

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...

. Aside from its laboratory function, the eudiometer is also known for its part in the " Volta pistol". Volta invented this instrument in 1777 for the purpose of testing the "goodness" of air, analyzing the

flammability A combustible material is a material that can burn (i.e., sustain a flame) in air under certain conditions. A material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort a ...

of gases, or to demonstrate the chemical effects of electricity. Volta's Pistol had a long glass tube that was closed at the top, like a eudiometer. Two electrodes were fed through the tube and produced a spark gap inside the tube. Volta's initial use of this instrument concerned the study of swamp

gases Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such ...

in particular. Volta's pistol was filled with

and another gas. The

homogeneous Homogeneity and heterogeneity are concepts relating to the uniformity of a substance, process or image. A homogeneous feature is uniform in composition or character (i.e., color, shape, size, weight, height, distribution, texture, language, i ...

mixture In chemistry, a mixture is a material made up of two or more different chemical substances which can be separated by physical method. It is an impure substance made up of 2 or more elements or compounds mechanically mixed together in any proporti ...

was taped shut with a cork. A spark could be introduced into the gas chamber by electrodes, and possibly

catalyze Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

a reaction by

static electricity Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it can move away by an electric current or electrical discharge. The word "static" is used to differentiate it from electric ...

, using Volta's

electrophorus In electromagnetism, an electrophorus or electrophore is a simple, manual, Capacitor, capacitive, electrostatic generator used to produce Electric charge, charge via the process of electrostatic induction. A first version of it was invented in 1 ...

. If the gases were

flammable A combustible material is a material that can burn (i.e., sustain a flame) in air under certain conditions. A material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort ...

, they would explode, and increase the

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

within the gas chamber. This pressure would be too great and eventually cause the cork to become airborne. Volta's pistol was made with either glass or brass, however due to the electricity the glass was vulnerable to exploding. Volta's extensive studies on measuring and creating high levels of electric currents caused the electrical unit, the

volt The volt (symbol: V) is the unit of electric potential, Voltage#Galvani potential vs. electrochemical potential, electric potential difference (voltage), and electromotive force in the International System of Units, International System of Uni ...

, to be named after him. In 1785

Henry Cavendish Henry Cavendish ( ; 10 October 1731 – 24 February 1810) was an English experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "inflammable air". He described the density of inflammable a ...

used a eudiometer to determine the fraction of oxygen in the Earth's atmosphere.

Etymology

The name "eudiometer" comes from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

meaning clear or mild, which is the combination of the

prefix A prefix is an affix which is placed before the stem of a word. Particularly in the study of languages, a prefix is also called a preformative, because it alters the form of the word to which it is affixed. Prefixes, like other affixes, can b ...

meaning "good", and meaning "heavenly" or "of Zeus" (the god of the sky and atmosphere), with the

suffix In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns and adjectives, and verb endings, which form the conjugation of verbs. Suffixes can ca ...

''-meter'' meaning "measure". Because the eudiometer was originally used to measure the amount of oxygen in the

air An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

, which was thought to be greater in "nice" weather, the root appropriately describes the apparatus.

Usage

Applications of a eudiometer include the analysis of gases and the determination of volume differences in chemical reactions. The eudiometer is filled with

, inverted so that its open end is facing the ground (while holding the open end so that no water escapes), and then submersed in a basin of water. A

chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...

is taking place through which gas is created. One reactant is typically at the bottom of the eudiometer (which flows downward when the eudiometer is inverted) and the other reactant is suspended on the rim of the eudiometer, typically by means of a

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

wire (due to their low reactivity). When the gas created by the chemical reaction is released, it should rise into the eudiometer so that the experimenter may accurately read the

of the gas produced at any given time. Normally a person would read the volume when the reaction is completed. This procedure is followed in many experiments, including an experiment in which one experimentally determines the

Ideal gas law The ideal gas law, also called the general gas equation, is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions, although it has several limitations. It was first stat ...

constant R. The eudiometer is similar in structure to the

meteorological Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agriculture ...

. Similarly, a eudiometer uses water to release gas into the eudiometer tube, converting the gas into a visible, measurable amount. A correct measurement of the pressure when performing these experiments is crucial for the calculations involved in the ''PV''=''nRT'' equation, because the pressure could change the

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

of the gas.

Description

History

Etymology

Usage

See also

References

Further reading