Hypothesis Dalton

Once they have detected patterns, scientists develop hypotheses, possible explanations of the laws—or the observations—in terms of more fundamental concepts. Observation requires careful attention to detail, but the development of a hypothesis requires insight, imagination, and creativity. In 1807, John Dalton interpreted experimental results to propose the hypothesis that matter consists of atoms. Although Dalton could not see individual atoms, he was able to imagine them and formulate his atomic hypothesis. Dalton s hypothesis was a monumental insight that helped others understand the world in a new way. The process of scientific discovery never stops. With luck and application, you may acquire that kind of insight as you read through this text, and one day you may make your own extraordinary hypotheses. 

Whereas Nature has been evolving the complexity of matter over the past 10 to 13 billion years, mankind formally began its journey directed at the science of abiotic synthesis only approximately 200 years ago. Beginning with Lavoisier s atom hypothesis Dalton s molecular hypothesis followed by the initiation of organic chemistry with Wohler s work, the progress of manmade synthetic evolution appears to be in its infancy compared to Nature s evolution [10,11]. 

The postulates of Dalton s atomic hypothesis are described in Section B. 

B.2 (a) Which part of Dalton s atomic hypothesis has been disproved by experiments (b) Summarize the evidence disproving this hypothesis. 

Atoms Humbug Rarely does a major new eoneept receive unanimous acceptance. Despite the atomie theory s impact, several major seientists denied the existence of atoms for another eentury. In 1877, Adolf Kolbe, an eminent organic chemisf said [Dalton s atoms are]. .. no more than stupid hallucinations. .. mere table-tapping and supernatural explanations. The influential physicist Ernst Mach believed that scientists should look at facts, not hypothetical entities such as atoms. It was not until 1908 that the famous chemist and outspoken opponent of atomism Wilhelm Ostwald wrote, I am now convinced [by recent] experimental evidence of the discrete or grained nature of matter, which the atomic hypothesis sought in vain for hundreds and thousands of years. (p.45)... 

Z. Jumps in knowledge arise from new theoretical concepts, such as the disproving of the phlogiston hypothesis ("the" paradigm shift) or the atom model of Dalton and the Periodic Table. An equally accelerating effect results from the discovery of new methods, such as electrochemistry, spectral analysis, and X-rays. 

John Dalton s Atomic hypothesis. J. Fraunhofer locates and names Fraunhofer lines A...L in solar spectrum. About the same time, Herschel discovers infrared radiation from the Sun. 

On the atom, see Alan J. Rocke, Chemical Atomism in the Nineteenth Century From Dalton to Cannizzaro (Columbus Ohio State University Press, 1984) Mary Jo Nye, "The Nineteenth-Century Atomic Debates and the Dilemma of an Indifferent Hypothesis," SHPS 7 (1976) 245268 and Mi Gyung Kim,... 

Alan Rocke claims that the advocacy of the method of hypothesis, which had been familiar to physicists for a generation, began to replace inductivist rhetoric in chemical circles just about the time that Kekule was formulating his benzene theory. But the method of hypothesis was a familiar one to chemical leaders like Berzelius and Dumas, and Dalton hardly avoids the fact of his hypothetical reasoning by his, indeed, inductivist rhetoric.51... 

Comparing and Contrasting Compare your hypothesis to Dalton s atomic theory. In what ways is it similar How is it different ... 

Although it was Daltons atomic hypothesis that first achieved the idealized goal of a true chemical calculus, the effort to acquire the requisite precision of data called for by Lavoisier had made substantial progress before 1808. Indeed without that accumulation of the empirical data, Daltons hypothesis would have carried no persuasion at all in a climate still dominated by an inductivist epistemology. 

Though Dalton had made these early estimates of relative atomic weights from chemical data, the foundation of his interests was still the physical nature of the gaseous state, and he soon became discontented with his first model of mixed gases according to which particles repelled only particles like themselves. This hypothesis, however beautiful might be its application, had some improbable features, he recalled retrospectively in 1810. These included the necessity for as many different kinds of repulsive forces as there were different kinds of gaseous atoms. It also meant the... 

But the potentiality of molecular structure could not be successfully pursued until the atomic weights were reliably established and the number of atoms in the molecules could be reliably known. This was not accomplished until fifty years later, by Stanislao Cannizzaro, through a rigorous application of Avogadros hypothesis first published in 1811. Since this long complex story does not involve any change in the compositional concepts introduced by Dalton, it is appropriate to offer only a brief account. 

John Dalton (1766-1844) lived and worked most of his life in Manchester, and he was a mainstay of that city s Literary and Philosophical Society. He had a life-long interest in the earth s atmosphere. Indeed, it was this interest that led him to study gases, out of which study grew his atomic hypothesis (2). His experiments on gases also led to a result now known as Dalton s law of partial pressures (5). Dalton s name is also linked to color blindness, sometimes called daltonism, a condition he described from firsthand experience. 

The laws of definite and multiple proportions are also associated with Dalton, for they can be explained by his atomic hypothesis. The law of definite proportions or of constant composition had previously been proposed in the work of Jeremias Richter and Joseph-Louis Proust. The law of multiple proportions came to be regarded as an empirical law quite independent of its relation to the atomic hypothesis or perhaps as an empirical law that inspired the atomic hypothesis however, Roscoe and Harden have shown that in Dalton s mind it was a testable prediction which followed from the atomic hypothesis 4). 

In my opinion, Mr. Dalton is too much of an Atomic Philosopher, and in making atoms arrange themselves according to his own hypothesis, he has often indulged in vain speculation. . . the essential and truly useful part of his doctrine. .. is perfectly independent of any views respecting the ultimate nature either of matter or its elements. 

DALTON DEFENDED HIS ATOMIC HYPOTHESIS AGAINST EXPERIMENTAL EVIDENCE... 

Gay-Lussac s results, illustrated in Figure 3.8b, showed that 2 liters of water vapor formed. So where did the atoms needed to create the additional liter of water vapor come from Did each hydrogen atom and each oxygen atom split in half This would effectively double the number of atoms, allowing for a second volume of water. The notion of an atom splitting in half, however, was counter to Dalton s well-received atomic hypothesis. 

Dalton understood Avogadro s creative argument but found it unacceptable because it failed to explain how two atoms of the same element could bond to each other. Based on his own research, Dalton had come to the erroneous conclusion that atoms of the same kind always have a natural repulsion for one another. Because of Dalton s authority in the scientific community, Avogadro s hypothesis was discarded and did not reappear for another half-century. 

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