New Evidence Suggests Origin of John Dalton’s Atomic Theory May Be Linked to Work of Irish Chemist Bryan Higgins
By Mark Grossman
It’s been quite a while since my last detailed post
to the Meteorite Manuscripts blog,
but for good reason — I took a rather circuitous route from researching
meteorites to becoming engaged in the origin of John Dalton’s atomic theory. My
road map, with all its twists and turns, is best addressed in a future post.
That being said, I am pleased to announce that a paper
of mine on the subject now appears in the December 2014 issue of Notes & Records: The Royal Society
Journal of the History of Science, and it raises new doubts about how John
Dalton came up with his atomic theory. Specifically, the paper provides the
first substantial evidence to challenge the conclusion, made by noted chemical
historian J. R. Partington in 1939 and adopted by others who followed, that
Dalton was not influenced by Irish chemist Bryan Higgins. Partington acknowledged that Dalton’s work
developed concepts first introduced by Higgins, stating “Dalton’s theory is,
therefore, not based on arbitrary rules but on the Newtonian atomic theory; it
is an extension of that of Bryan Higgins and makes use of similar ideas...” But Partington
ruled out the possibility of any influence, continuing “although there is no
reason to think that Dalton was indebted to Higgins.” My paper does indeed
provide evidence to suggest a “missing link” between Dalton and Bryan Higgins
— it is William Allen —Dalton’s friend, fellow Quaker, and chemist.
Dalton first described his atomic theory in his book
A New
System of Chemical Philosophy, published in 1808. His theory, based on principles
such as the uniqueness of atoms of the same element, relative atomic masses, and
the rules of chemical combination, comprise the tablets of modern chemistry, enabling
present-day chemists to perform a myriad of practical calculations, without
giving a second thought as to their origin.
John Dalton
In spite of the magnitude of his accomplishment, how
Dalton came up with his theory remains a mystery, which has been debated by
historians for over 150 years. Although it is clear that his interests
in meteorology, evidenced in his 1793 book Meteorological
Observations and Essays, fueled his investigations, did his atomic theory
arise from work on chemical combination or from investigation of solubility of
gases in water? Amidst the debate regarding
the origins, the possibility that Dalton was influenced by, or even aware of,
the theories of Irish chemists Bryan and William Higgins, uncle and nephew,
respectively, has been given little credence.
In How John Dalton's meteorological studies led to the
discovery of atoms, a YouTube video published by the Chemical Heritage
Foundation in May 2013, Arnold Thackray, eminent Dalton scholar and founder of CHF,
describes the standard narrative of how Dalton’s chemical atomic theory
emerged from his meteorological interests. Thackray, holding a letter written
by Dalton, who resided in Manchester in 1803, comments:
“By the time we get from his Meteorological Observations in 1793 to his 1803 letter in
Manchester, he’s talking about ‘the new chemical doctrine I have lately
promulgated.’ He’s on to something, and he’s developing a whole theory of
chemistry, of atoms, of what they might be.”
[2:41 in video below]
Arnold Thackray of the Chemical Heritage Foundation
The letter which Thackray mentions in the video was
written by Dalton on 12 April 1803, and the full text, which appeared in the November
2010 issue of the journal Ambix,
shows that Thackray, perhaps due to time constraints of the video clip, only referenced
the first sentence of the relevant paragraphs. The text actually reads as follows:
“The new chemical doctrines I have lately promulgated have been much
circulated on the continent in the Annales
de Chimie, &c, & highly spoken by Berthollet, Pictet, &c. Mr.
Wm. Henry here has declared his adoption of them, and I infer no opposition
from any quarter. Every days experience convinces me of their stability.
I am just about the point of discovering something superior to any of
those already published, & which may be of as much importance to science as
that of Gravitation itself — I mean the nature of Heat & all its
combinations with substances.”
In the first paragraph of the letter, Dalton is
referring to the French scientific journal that published his work on the law
of partial pressures, steam, evaporation, and the expansion of gases, not
his atomic theory based on rules of chemical combination or relative atomic masses.
As indicated by the next paragraph in his letter, Dalton was “on to something”
alright, but it had nothing to do with chemical combination or atomic masses —
it was heat, and how it combined with
matter. Throughout his life, Dalton
believed in caloric, the supposed substance of heat at the time.
So where does William Allen fit into the picture? Allen
was the son of a silk weaver, who ended up running a chemical/pharmaceutical
business at Plough Court (which became Allen & Hanburys, and much later part
of GlaxoSmithKline). His interest in chemistry was fueled by his association
with Bryan Higgins. In a recap of the year 1793, he notes in his diary “I have
attended some of Higgins’s lectures, — learnt something of short-hand, and the
new system of chemistry, and instituted a plan for my future studies.” The following
year, he became a member of Higgins’s Society for Philosophical Experiments and
Conversations, and at the close of 1794, he volunteered to serve on the
Committee of Publication to oversee the distribution and expense of the Minutes of the Society, which were
written up by Higgins. As such, Allen would have been thoroughly conversant
with Higgins’s theories, which focused so much on heat, Partington declared: “The Minutes
of the Society dwells in tedious detail on the nature of ‘caloric.’”
William Allen
On 10 July 1803, Dalton traveled to London to talk with
Allen about his friend’s prospects for lecturing at the Royal Institution.
Although the meeting between the two men occurred at a crucial moment in the
narrative of the origin of the atomic theory, it has not been noticed or addressed
by Dalton scholars. Dalton believed his new investigations on heat could be as important
as the law of gravity, and he certainly would have discussed this with his friend
Allen, just as he had mentioned it in the 12 April 1803 letter cited above. How could Allen remain silent when Dalton began to talk about “the
nature of Heat & all its combinations with substances”, when one of the
first, fundamental lectures described in the Minutes of the Society,
was “Caloric, whose Parts are repellent of each other, combines with divers
Bodies”? To me, it is difficult to believe that Dalton could possibly emerge
from his meeting with Allen without learning something of Higgins’s theories.
But why is Bryan Higgins’s theory of heat so important
to the origin of Dalton’s atomic theory? According to Higgins, matter consisted
of globular atoms surrounded by a repelling atmosphere of heat, and it was the
balance of the repulsive and attractive forces between atoms that led to their
combination, one atom to another, a process Higgins called “saturation.” Although
Higgins’s examples of saturation dealt with binary combinations of atoms, in at
least one instance in his Minutes of the
Society, he did allude to combination of more than two particles to form
ternary or higher compounds. One of the key foundations of Dalton’s atomic
theory is his “rule of greatest simplicity,” a binary combination of atoms,
similar to Bryan, but applied step-by-step to form ternary and compounds of
higher order, which Dalton used to explain his law of multiple proportions.
Assuming my arguments are correct, Dalton’s visit
with Allen, where he was exposed to Higgins’s ideas on combination and
saturation, could explain why Dalton was able to come up with his theory of multiple
proportions so quickly after he began his first chemical investigations. Sure enough, on 4 August 1803, just about
three weeks after his meeting with Allen, Dalton described the first
experimental evidence illustrating the law in his notebook:
"It appears, too, that a very rapid mixture of equal
parts com. air and nitrous gas, gives 112 or 120 residuum. Consequently that
oxygen joins to nit. gas sometimes 1.7 to 1, and at other times 3.4 to 1."
Several historians have suggested that Dalton was
specifically looking for evidence of multiple proportions in his experimental
data, and various reasons have been offered as to how he made such rapid
progress in developing his chemical atomic theory. In light of the evidence
provided in my paper, I believe that Dalton’s meeting with Allen, where he
learned of Higgins’s theory of heat and chemical combination, provides the
simplest and most logical explanation.
Exactly how and to what extent Bryan Higgins’s
theories might have influenced Dalton are questions certainly open to debate.
But Dalton’s ideas did resemble Higgins’s in many respects, and I believe his meeting
with Allen represents a "missing link" in the development of the atomic theory,
a "Daltonian doubt" regarding Bryan Higgins, but one not as easily resolved as
the “Daltonian doubts” floated by historians over the past 50 years for other scientists
who might have influenced Dalton.
For a more detailed discussion with references, see M. I. Grossman, “John Dalton and the London Atomists: William and Bryan Higgins, William
Austin, and New Daltonian Doubts about the Origin of the Atomic Theory”, Notes & Records: The Royal Society
Journal of the History of Science 68(4),
339-356 (2014), by searching for the article title at the journal hompage at http://rsnr.royalsocietypublishing.org/,
or at http://rsnr.royalsocietypublishing.org/content/68/4/339.full.pdf+html.
The paper also argues that Dalton should have been aware of William Higgins’s
work before he came up with his first table of atomic weights, and briefly
addresses the possible influence of British physician/chemist William Austin on
Dalton’s thinking regarding relative atomic masses — topics that are beyond
the scope of the current post.
