Sunday, November 30, 2014

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 atomsa 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, or at 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.    

Copyright © M. I. Grossman  

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