A eudiometer is a laboratory device that measures the change in volume of a

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

mixture following a physical or chemical 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, 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 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 with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Platin ...

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 ionized, electrically conductive channel through a normally-insulating medium, often air or other gases or gas mixtures. Michael ...

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, natural philosopher, separatist theologian, grammarian, multi-subject educator, and liberal political theorist. He published over 150 works, and conducted exp ...

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 it ...

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,

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

, and

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

. He also discovered a way to find the purity or "goodness" of air using "nitrous air test". The eudiometer functions on the greater solubility 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 Marsilio Landriani (Milan, 1751 – Vienna, 1815) was an Italian chemist, physicist and meteorologist. He became known with his first book, (Physical investigations on the salubrity of air), published in 1775. In it he described a new instrumen ...

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, the former ''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, dedica ...

An associate of Moscati's,

Felice Fontana Abbé Gasparo Ferdinando Felice Fontana (15 April 1730 – 9 March 1805) was an Italian polymath who contributed to experimental studies in physiology, toxicology, and physics. As a physicist he discovered the water gas shift reaction in 1780. He ...

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 (or John) Ingenhousz or Ingen-Housz FRS (8 December 1730 – 7 September 1799) was a Dutch-born British physiologist, biologist and chemist. He is best known for discovering photosynthesis by showing that light is essential to the process ...

verified that the bubbles given off under water by plant leaves exposed to sunlight were oxygen bubbles. His description of photosynthesis was published in 1779, and in 1785 he wrote about eudiometers in ''

Journal de Physique The ''European Physical Journal'' (or ''EPJ'') is a joint publication of EDP Sciences, Springer Science+Business Media, and the Società Italiana di Fisica. It arose in 1998 as a merger and continuation of ''Acta Physica Hungarica'', '' Anales de ...

'' (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 physicist, chemist and lay Catholic who was a pioneer of electricity and power who is credited as the inventor of the electric battery and the ...

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

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...

. Aside from its laboratory function, the eudiometer is also known for its part in the "

Volta pistol Volta may refer to: Persons * Alessandro Volta (1745–1827), Italian physicist and inventor of the electric battery, count and eponym of the volt * Giovanni Volta (1928–2012), Italian Roman Catholic bishop * Giovanni Serafino Volta (1764–1 ...

". Volta invented this instrument in 1777 for the purpose of testing the "goodness" of air, analyzing the

flammability A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...

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 in particular. Volta's pistol was filled with oxygen and another gas. The homogeneous mixture was taped shut with a cork. A spark could be introduced into the gas chamber by electrodes, and possibly

catalyze Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

a reaction by

static electricity Static electricity is an imbalance of electric charges within or on the surface of a material or between materials. The charge remains until it is able to move away by means of an electric current or electrical discharge. Static electricity is na ...

, using Volta's

electrophorus In electromagnetism, an electrophorus or electrophore is a simple, manual, capacitive, electrostatic generator used to produce charge via the process of electrostatic induction. A first version of it was invented in 1762 by Swedish professor Jo ...

. If the gases were

flammable A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...

, they would explode, and increase the pressure 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, to be named after him. In 1785 Henry Cavendish used a eudiometer to determine the fraction of oxygen in the Earth's atmosphere.

Etymology

The name "eudiometer" comes from the Greek meaning clear or mild, which is the combination of the prefix meaning "good", and meaning "heavenly" or "of Zeus" (the god of the sky and atmosphere), with the suffix ''-meter'' meaning "measure". Because the eudiometer was originally used to measure the amount of oxygen in the

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...

, 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 water, 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 chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breakin ...

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

or copper 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 volume 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 constant R. The eudiometer is similar in structure to the

meteorological Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...

. 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 of the gas.

Description

History

Etymology

Usage

See also

References

Further reading