In thermochemistry, specific heat, an early synonym of heat capacity, refers to the amount of heat, specific to each body, absorbed or released, requisite to raise or lower the temperature of the body by a certain number of degrees.

Overview
In 1760, Scottish chemist Joseph Black, noted student of evaporative cooling research chemist William Cullen, according to American science historian Frederic Holmes, had discovered the concepts of both latent heat and specific heat, but did not formerly publish on these subjects; accordingly, his views only gradually became known vicariously through his students, associates, and lectures. [8]

To cite one example, in a series of 1780 letters to Black's student James Watt, Portuguese physicist Joao Magellan, who is often credited with having coined the term "specific heat", attacked Black for his failure to publish his own work on heat. [2] Another of Black's students was Irish chemist and physician William Irvine, who in the 1770s developed a theory of heat based on Black’s discoveries, using a concept of “absolute heat”, differing from Black’s ideas to some extent. [9]

Likewise, Irish chemist Adair Crawford, after hearing Irvine lecture at Glasgow, developed a method for measuring specific heats, which following Irvine, he called “heat capacities”, wherein he mixed two different substances, initially at different temperatures, and from the final temperature and masses he could calculate their respective specific heats. [8] Crawford, in his 1779 book Experiments and Observations on Animal Heat, outlined experiments for determining what he called the “absolute heat” of bodies, which are said to have been the same methods as described by Magellan in 1780. [4]

Some references trace the coining of the term "specific heat" to the circa 1777 work of Irish chemist Richard Kirwan, who used the term "specific fire" as well as bodies having a "capacity" for the "matter of fire" (phlogiston), which it was argued could flow into or out of bodies by the path of least resistance. This usage was adopted by Magellan, as found in his 1780 table of specific heats, who credits Kirwan for his data.

Others, however, cite the work of Swedish chemist Johan Wilcke who in the late 1770s was doing calorimetry work and in 1782 published a paper entitled "On Specific Heat". [5] Some claim that Wilcke's employed the name "specific heat" modeled on the earlier usage of "specific gravity". [6]

Kopp summarizes, that aside from the investigations of Wilke and Crawford, others such as Black and Irvine were among to do the earliest investigations and that Antoine Lavoisier and Pierre Laplace were the ones to introduce ice calorimetry as a method for determining the specific heats of bodies.

In 1865, German chemist Hermann Kopp, summarized the gist of the conception of specific heats, as follows: [3]

“About the year 1780 it was distinctly proved that the same weights of different bodies require unequal quantities of heat to raise them through the same temperature, or give out unequal quantities of heat on cooling through the same number of thermometric degrees. It was recognized that for different bodies the unequal quantities of heat, by which the same weights of different bodies are heated through the same range, must be determined as special constants, and considered as characteristic of the individual bodies. This newly discovered property of bodies, Wilcke designated as their specific heat, while Crawford described it as the comparative heat, or as the capacity of bodies for heat.”

American thermodynamicist Merle Potter (2011) asserts that the following equation:

Specific heat (constant volume)

where Q is heat added to a body, m is the mass of the body, Cv is the heat capacity at constant volume, and ΔT is the temperature change of the body, was the first specific heat equation (fact check). [11]

This quote, referring to the work of Irish chemist Adair Crawford (1748-1795) and Swedish chemist Johann Wilcke (1732-96), succinctly captures a rather detailed history of research on a phenomenon of heating and cooling bodies discovered by Scottish chemist Joseph Black in circa 1760.

The following table gives a chronology of the terms "specific heat" and "heat capacity" (or "capacity of bodies for heat") used over the years:

Table of Specific Heat Synonyms
(terminologies, usages, and coinages)

Name
Date
Person





?1760Joseph Black (1728-1799) Scottish physicist and chemist
Absolute heat1770sWilliam Irvine (1743-1787) Irish chemist and physician
Specific firec.1777Richard Kirwan (1733-1812) Irish chemist
Capacity of bodies for receiving the matter of heatc.1777Richard Kirwan
Absolute heat of bodies1779Adair Crawford (1748-1795) Irish chemist
Specific heat1780Joao Magellan (1722-1790) Portuguese physicist
Specific heat1782Johan Wilcke (1732-96) Swedish chemist
Capacities [of substances] for heat1807Thomas Young (1773-1829) English polymath
Caloric specific 1824Anon, Dictionary of Chemistry
Capacity for heat / Specific heat1846Karl Friedrich Peschel
Heat-capacity1848Leopold Gmelin (1788-1853) German chemist
Specific heat | Capacity of bodies for heat1860John Johnston
Specific heat (capacity for heat referred to a given weight)1861Leopold Gmelin
Specific heat [Capacity for heat]1865Rudolf Clausius (1822-1888) German physicist
Real specific heat [Real capacity for heat]1865Rudolf Clausius
Specific heat capacity1869Anon, Nature, Vol. 290
Specific heat-capacity1880James Hamblin Smith, An Introduction to the Study of Heat
Heat capacity1894Wilhelm Ostwald

Into the late 1880s, the phrase "specific heat capacity" seems to have come into common usage, as did "heat capacity", a shorthand version of the former, in the 1890s. Some references, in the 1890s, to note, began to differentiate as follows: [10]

● Capacity for heat (Irvine) of a body is the number of units of heat required to raise one pound weight of the body one degree in temperature.
● Specific heat (Gadolin) of a body is its capacity for heat compared with that of an equal weight of water.

These types of definitions, however, only seem to only compound the proliferation of confusion on the mixed usage of terminology on this concept.

Magellan | Specific heat table
Many references attribute the introduction of the term “specific heat” to 1780 publication “Essay on a New Theoretical Law of the Fire Element, and of the Heat of Bodies” by Portuguese physicist Joao Magellan, which contained a table of specific heats. [1] Magellan, however, credits the data of his table to Irish chemist Richard Kirwan, who since 1777 had been working on heat measurements in London, in support of his phlogiston theories.

Kirwan | Specific fire
Kirwan, in his 1787 publications, defined the term specific fire as such: [2]

“All bodies require a certain quantity of elementary fire or light to heat them to a certain degree, but the quantity requisite to produce this degree varies, according to the nature of the species of these bodies, and hence the proportion suited to each is called their specific fire; the more of this any species of bodies requires, the greater time it will require, in the same circumstances, either to acquire or to lose it, that is, either to heat or to cool.”

In other words, the term “specific” seems to have been introduced into heat theory as a way to say that each body varies, in a specific way, as to the rate at which it may be heated or cooled by the addition or removal of heat, hence each body as a specific nature to it in regards to how it responds to heating or cooling, as measured by changes in degrees. The way in which Kirwan used the term here, to note, is in the sense that each body will require a certain addition or removal of phlogiston to produce a change of degree, in the sense that phlogiston, the "element of fire", is a substance that can be added or removed from bodies.

Kirwan | Capacity for the matter of heat
That same year, 1787, on the topic of evaporation of liquids by heat, in the context of each body having a certain “capacity” for receiving the matter of heat, Kirwan states: [2]

“The next general source of cold is evaporation; for the attraction of the particles of liquids decreases as their points of contact diminish, and thereby their capacity for receiving the matter of heat, (which is the same as that of light) increases; by this increased capacity, the matter of heat or fire contained in the neighboring bodies, which, like all other fluids, flows where it finds least resistance, is determined to flow towards the vapor; and consequently those bodies are cooled, though the vapor is not heated; because the reaction of its particles is barely equal to that which it had before its capacity was increased.”

The exact years in which "specific heat" was replaced by "specific heat capacity" and then by "heat capacity", in its modern usage, remains to be determined.

References
1. (a) Magellan, Joao. (1780). “Essay on a New Theoretical Law of the Fire Element, and of the Heat of Bodies” (“Essai sur law Nouvelle Theorie du Feu Elementaire, et de la Chaleur des Corps”). London.
(b) Scott, E.L. (1981). “Richard Kirwan, J. H. de Magellan, and the Early History of Specific Heat” (abs). Annals of Science, 38(2): 141-53.
2. Kirwan, Richard. (1787). An Estimate of the Temperature of Different Latitudes (capacity [for matter of heat], pg. 12; specific fire, pg. 38). London: J. Davis.
3. Kopp, Hermann. (1865). “Investigations of the Specific Heat of Solid Bodies”, Journal of the Chemical Society, 4(19): 154-234.
4. (a) Crawford, Adair. (1779). Experiments and Observations on Animal Heat, and the inflammation of Combustible Bodies: Being an Attempt to Resolve these Phenomena into a General Law of Nature (1788 second edition). London: J. Johnson.
(b) McKie, Douglas and Heathcote, Niels. (1975). The Discovery of Specific and Latent Heats (specific heat, 30+ pgs; Crawford, 15+ pgs). Arno Press.
5. (a) Wilke, Johan. (1782). “On Specific Heat”, N. Abhandl. D. Schwed. Akad. D. Wiss. 2: 489.
(b) Dickinson, Hobert. (1915). Combustion Calorimetry (Wilke: author of the term “specific heat”, pg. 264). Govt. Print. Off.
6. Wilcke, Johann. (1782). “On Specific Heat”, N. Abhandl. D. Schwed. Akad. D. Wiss. 2: 489.
7. Hankins, Thomas L. (1985). Science and the Enlightenment (Johann Carl Wilcke (1732-96), pg. 75). Cambridge University Press.
8. Holmes, Frederic L. (1987). Lavoisier and the Chemistry of Life: an Exploration of Scientific Creativity (Black, latent heat and specific heat, pg. 158). University of Wisconsin Press.
9. Stephen, Leslie and Lee, Sidney. (1922). Dictionary of National Biography (William Irvine, M.D. (1743-1787), pg. 50). Oxford University Press.
10. Adams, Henry. (1897). Handbook for Mechanical Engineers (pg. 173). Spon.
11. Potter, Merle C. and Somerton, Craig W. (2009). Schaum's Outlines: Thermodynamics for Engineers (pg. 72). McGraw-Hill.

External links
● Specific heat - Eric Weisstein's World of Science.

TDics icon ns