Antoine Lavoisier in the context of "Phlogiston"

Nitrogen is a chemical element; it has symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N₂, a colourless and odourless diatomic gas. N₂ forms about 78% of Earth's atmosphere, making it the most abundant chemical species in air. Because of the volatility of nitrogen compounds, nitrogen is relatively rare in the solid parts of the Earth.

It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772 and independently by Carl Wilhelm Scheele and Henry Cavendish at about the same time. The name nitrogène was suggested by French chemist Jean-Antoine-Claude Chaptal in 1790 when it was found that nitrogen was present in nitric acid and nitrates. Antoine Lavoisier suggested instead the name azote, from the Ancient Greek: ἀζωτικός "no life", as it is an asphyxiant gas; this name is used in a number of languages, and appears in the English names of some nitrogen compounds such as hydrazine, azides and azo compounds.

In chemistry and thermodynamics, calorimetry (from Latin calor 'heat' and Greek μέτρον (metron) 'measure') is the science or act of measuring changes in state variables of a body for the purpose of deriving the heat transfer associated with changes of its state due, for example, to chemical reactions, physical changes, or phase transitions under specified constraints. Calorimetry is performed with a calorimeter. Scottish physician and scientist Joseph Black, who was the first to recognize the distinction between heat and temperature, is said to be the founder of the science of calorimetry.

Indirect calorimetry calculates heat that living organisms produce by measuring either their production of carbon dioxide and nitrogen waste (frequently ammonia in aquatic organisms, or urea in terrestrial ones), or from their consumption of oxygen. Lavoisier noted in 1780 that heat production can be predicted from oxygen consumption this way, using multiple regression. The dynamic energy budget theory explains why this procedure is correct. Heat generated by living organisms may also be measured by direct calorimetry, in which the entire organism is placed inside the calorimeter for the measurement.

Henry Cavendish (/ˈkævəndɪʃ/ KAV-ən-dish; 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 air, which formed water on combustion, in a 1766 paper, On Factitious Airs. Antoine Lavoisier later reproduced Cavendish's experiment and gave the element its name.

A shy man, Cavendish was distinguished for great accuracy and precision in his researches into the composition of atmospheric air, the properties of different gases, the synthesis of water, the law governing electrical attraction and repulsion, a mechanical theory of heat, and calculations of the density (and hence the mass) of the Earth. His experiment to measure the density of the Earth (which, in turn, allows the gravitational constant to be calculated) has come to be known as the Cavendish experiment.

Jean-Antoine Chaptal, comte de Chanteloup (French pronunciation: [ʒɑ̃ ɑ̃twan ʃaptal]; 5 June 1756 – 29 July 1832) was a French chemist, physician, agronomist, industrialist, statesman, educator and philanthropist.

Chaptal was involved in early industrialization in France under Napoleon and during the Bourbon Restoration. He was a founder and the first president of the Society for the Encouragement of National Industry. He was an organizer of industrial expositions held in Paris. He compiled a study surveying the condition and needs of French industry in the early 1800s. Chaptal published practical essays on the uses of chemistry. He was an industrial producer of hydrochloric, nitric and sulfuric acids, and was sought after as a technical consultant for the manufacture of gunpowder. Chaptal published works which drew on Antoine Lavoisier's theoretical chemistry to make advances in wine-making. Chaptal promoted adding sugar to increase the final alcohol content of wines, now referred to as "chaptalization".

Baron Jöns Jacob Berzelius (Swedish: [jœns ˈjɑ̌ːkɔb bæˈʂěːlɪɵs]; 20 August 1779 – 7 August 1848) was a Swedish chemist. Berzelius is considered, along with Robert Boyle, John Dalton, and Antoine Lavoisier, to be one of the founders of modern chemistry. Berzelius became a member of the Royal Swedish Academy of Sciences in 1808 and served from 1818 as its principal functionary. He is known in Sweden as the "Father of Swedish Chemistry". During his lifetime he did not customarily use his first given name, and was universally known simply as Jacob Berzelius.

Although Berzelius began his career as a physician, his enduring contributions were in the fields of electrochemistry, chemical bonding and stoichiometry. In particular, he is noted for his determination of atomic weights and his experiments that led to a more complete understanding of the principles of stoichiometry, which is the branch of chemistry pertaining to the quantitative relationships between elements in chemical compounds and chemical reactions and that these occur in definite proportions. This understanding came to be known as the "Law of Constant Proportions".

A calorimeter is a device used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber. It is one of the measurement devices used in the study of thermodynamics, chemistry, and biochemistry.

To find the enthalpy change per mole of a substance A in a reaction between two substances A and B, the substances are separately added to a calorimeter and the initial and final temperatures (before the reaction has started and after it has finished) are noted. Multiplying the temperature change by the mass and specific heat capacities of the substances gives a value for the energy given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction.$${\displaystyle q=C_{\text{v}}(T_{f}-T_{i}),}$$ where q is the amount of heat according to the change in temperature measured in joules and C_v is the heat capacity of the calorimeter which is a value associated with each individual apparatus in units of energy per temperature (joules/kelvin).