|A 1971 article on independent molecular sociology themed work of Roy Henderson and Elihu Fein, who applied physics and thermodynamics to questions of social phenomena. |
“Between the method of Quetelet, who represents, so to speak, molecular sociology, and that of Comte, who especially represents synthetic sociology, Spencer takes the mean, which, although it is without the qualities of the first, is also without the qualities of the first, is also without the dangers of second.”— Guillaume de Greef (1902), “Introduction to Sociology” 
The term “molecular sociology” is a synonym, essentially, to the terms social chemistry (Thomas Huxley, 1871) and human chemistry (1851, E.B.).
Henderson | Fein
In 1971-72, New Scientist magazine published a two-part article on “Molecular Sociology” in discussing the question “do people behave like molecules?” In the first installment of the article, in answer to this question, they state that “the success of two recent attempts to analyze human behavior using the established laws of molecular motion and of thermodynamics might suggestion so.” 
In particular, they discuss the highly-cited 1971 article “The Statistics of Crowd Fluids”, by Austrian mechanical engineer Roy Henderson, at the University of Sydney, who measured the movements of college students on a campus and children on a playground, finding that in both cases their movements fit the Maxwell-Boltzmann distribution, meaning that both velocities of gas particles and the speeds of students follow a Gaussian distribution.  Henderson found that crowds generally conform to the gas particle model, but found differences, such as that “men and women cannot be considered as ‘identical particles’.
The article also cites the article 1970 “Demography and Thermodynamics” by American physicist Elihu Fein, who finds, though examination of factors such as per capita income, that social activity is analogous to molecular activity, and applies concepts such as entropy and adiabatic to social systems.  Fein, however, cautions his readers, in that although his analogies seem to have validity, he emphatically states that “the conclusion is not that people act like molecules”, but that the goal is to understand ourselves and the world through abstract concepts.
Curiously, both the 1971 and 1972 New Scientist articles on molecular sociology also cites a person by the name of Daedalus who is said to have “developed a ‘molecular sociology’ an analogy between people and molecules [who] identified wealth in people with energy in molecules; [and] is now developing a financial thermodynamics or thermodynamics of money.” 
Goethe | Lehn
In 1991, when University of Twente, Netherlands, awarded French chemist Jean-Marie Lehn an honorary doctorate he told a highly evocative story about the discipline, which he described as "Molecular Sociology”, stating the following: (Ѻ)
“Just like with humans, we can ascribe characteristics to molecules. One type happily associates with one another, the other prefers to isolate itself.”
In 1995, Lehn, in his Supramolecular Chemistry, made reference to Goethe’s 1809 human elective affinities theory as being a type of ‘molecular sociology’, an analog to supramolecular chemistry: 
“Supramolecular chemistry is a sort of molecular sociology! Non-covalent interactions define the inter-component bond, the action and reaction, in brief, the behavior of the molecular individuals and populations: their social structure as an ensemble of individuals having its own organization; their stability and their fragility; their tendency to associate or to isolate themselves; their selectivity, their ‘elective affinities’ and class structure, their ability to recognize each other; their dynamics, fluidity or rigidity or arrangements and of castes, tensions, motions, and reorientations; their mutual action and their transformations by each other.”
Lehn here, of course, is culling from German polymath Johann Goethe's 1809 Elective Affinities.
In 1984, Belgian chemist Ilya Prigogine, in his 1984 Order Out of Chaos, mentions Goethe’s ‘Mittler the mediator’ as being a type of human catalyst, bring about successful reactions between people, without being consumed in the process. The concept of molecular sociology, with the introduction of the chemical thermodynamics work of Willard Gibbs (1876) and Hermann Helmholtz (1882), after which the measurement of affinity became a function of enthalpy change and entropy change, however, would move the subject of molecular sociology into the field of thermodynamics.
1. Staff. (1971). “Molecular Sociology Arrives at Last”, New Scientist, pg. 286. Feb 11.
2. Henderson, L. F. (1971). “The Statistics of Crowd Fluids”, Nature, 229: 381-83.
3. Fein, Elihu. (1970). “Demography and Thermodynamics”, American Journal of Physics, Vol. 38, pg. 1373.
4. Staff. (1972). “Ariadne”, New Scientist (molecular sociology, pg. 165), Vol. 20. Apr
5. Lehn, Jean-Marie. (1995). Supramolecular Chemistry (pg. 2). VHC.
5. Greef, Guillaume de. (1903). “Introduction to Sociology” (translated by Robert Morris) (molecular sociology, pgs. 511-12, 515, 592, 615), The American Journal of Sociology, 8(5):577-622.
● What are the dimensions of molecular sociology? (2013) – ResearchGate.net.