Great problem of chemical affinity

In science, great problem of chemical affinity refers to the ancient puzzle as to the nature of the chemical reaction, i.e. why certain things react together, whereas others don't, and what is the nature or measurement of the driving force of a chemical reaction.

In 1692, Newton wrote the draft notes for his "Query 31", wherein he he outlined the chemical force tendencies when different chemical entities are put in contact.

Prior to 1919, a knowledge of the specific heats of substances, near absolute zero, such as worked on by Walther Nernst and his pupils, was said to be essential towards a complete solution of the problem of chemical affinity. [2]

In 1923, American physical chemist Gilbert Lewis stated the following about the problem: [3]

“Indeed, our purpose at the outset (1909) was to merely to collect, for the practical use of the chemist and the chemical engineer, the data which we have obtained, or which we have assembled from the work of other investigators, pertaining to the ‘great problem of chemical affinity.’ But then we were convinced that mere reference tables would hardly render full service without some description of the methods by which they were obtained. The development of these methods of applying thermodynamics to chemical problems has occupied the greater part of our time for many years (1909-23) (14-years).”

Lewis' effort, in turn, would go on to become the most referenced thermodynamics textbook of the 20th century, and result eventually to replace the word “affinity” by the word “free energy” throughout the English speaking world. [4]

In 1949, Frederick Philbrick, et al, summarized things as follows: [1]

“By studying the energy relations of chemical change it is possible to understand much that must otherwise remain obscure, and in particular to form some ideas of the great problem of chemical affinity: why will substance A react with substance B but not with substance C?”

The latter part of this statement, of course, is Geoffroy's first law of affinity (1718), itself culled from Isaac Newton’s famous Query 31, together which became the seed for the construction of affinity tables (1718-c.1800), and the later 18th, 19th century versions of affinity chemistry, which gave way eventually to chemical thermodynamics (1876-onward), and modern chemical thermodynamics (1923-onward).

See also
Great problem of natural philosophy

1. Philbrick, Frederick A. Holmyard, Eric J., and Palmer, William. (1949). A Text Book of Theoretical & Inorganic Chemistry (pg. 220). Dent.
2. Dushman, Saul. (1914). “Recent Views on Matter and Energy” (great problem of chemical affinity, pg. 955)., General Electric Review, 17: 952-60.
3. Lewis, Gilbert N. and Randall, Merle. (1923). Thermodynamics and the Free Energy of Chemical Substances (pg. viii). McGraw-Hill Book Co., Inc.
4. Leicester, Henry M. (1956). The Historical Background of Chemistry (pg. 206). Dover.

Further reading
● Thims, Libb. (2007). Human Chemistry (Volume Two) (pg. 376). Morrisville, NC: LuLu.

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