Thomas Midgley, Jr., and the Development of New Substances: A

Article pubs.acs.org/jchemeduc

Thomas Midgley, Jr., and the Development of New Substances: A Case Study for Chemical Educators Hélio Elael Bonini Viana and Paulo Alves Porto* Grupo de Pesquisa em História da Ciência e Ensino de Química, Instituto de Química, Universidade de São Paulo, São Paulo 05508, Brazil ABSTRACT: This paper presents a history of chemistry case study focusing on selected aspects of the work of American engineer Thomas Midgley, Jr. (1889−1944): the development of tetraethyl lead as an antiknock gasoline additive and of chlorofluorocarbons (CFCs) as fluids for refrigeration devices. One general aim of this case study is to display the complex nature of science, including the relation of science to technological and social issues, the nonlinear and noncumulative nature of its development, and the contribution of people with different backgrounds to the construction of scientific knowledge. Moreover, this work focuses on promoting reflections about two main themes: the periodic table as a tool for chemists’ work and the ethical issues related to chemical risks. This case study may help chemistry teachers to enlarge and enrich their views on chemistry as a science and as a profession and to discuss such issues with students. KEYWORDS: Upper-Division Undergraduate, History/Philosophy, Problem Solving/Decision Making, Periodicity/Periodic Table, Ethics

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to teaching. Brito et al.11 showed some implications of a historical approach to the teaching of the periodic table, and several recent papers suggest different ways to discuss the periodic table at different educational levels.12−16 Our case study proposes yet another approach: to show the decisive role of the periodic table to Midgley’s professional achievements, which may serve as inspiration for chemistry teachers to find ways of helping students understand the significance and utility of this tool in the work of chemists. The second feature highlighted in this case study is the necessity of taking ethics into consideration when dealing with chemistry. The relevance of discussing ethical issues in the education of professional chemists already has been pointed out by Coppola and Smith,17 Kovac,18 Jacob and Walters,19 Eriksen,20 and Sjöström.21 Among the several ethical questions raised by undertaking chemical activities, this case study suggests reflections on how chemists deal with the risks involved in the manipulation of chemicals, especially when developing new substances that may have practical uses but whose potential risks are not fully understood. The case study presented here may help chemistry teachers enlarge and enrich their views on chemistry as a science and as a profession.

INTRODUCTION History and the philosophy of science have been recognized as being capable of offering important contributions to pre-service and in-service education of science teachers.1 However, the process of bringing this ideal from the realm of proposals to reality has many obstacles.2 One of these obstacles is the scarcity of didactic materials designed according to an updated approach to the history of science and in line with current educational goals. We agree with Allchin3 and Martins,4 who argue that an in-depth discussion of a case study in the history of science is more relevant, in the didactic context, than the mere mention of a great number of isolated names, dates, episodes, and anecdotes. Inclusion of historical case studies in science teaching may be done in many ways,5−8 and different approaches are possible, depending on the educational goals and educational levels.9 In this paper, we develop a case study on the history of chemistry by focusing on aspects of the work of Thomas Midgley, Jr. (1889−1944). The sources used in this research include papers published by Midgley in the 1930s and secondary sources. This case study may give rise to different reflections in different educational levels; however, our main concern here is to suggest its use in the pre-service or in-service education of chemistry teachers. One general aim of this case study is to display the complex nature of science, including aspects such as the relation of science to technological and social issues, the nonlinear and noncumulative nature of its development, and the contribution of people with different backgrounds to the construction of scientific knowledge. Chemical educators may even find other implicit points worth discussing with their students. Moreover, this work focuses on promoting reflections about two main themes: the periodic table as a tool for chemists’ work and the ethical issues related to chemical risks. Scerri10 has already pointed out the importance of the periodic table to chemical activities and also © XXXX American Chemical Society and Division of Chemical Education, Inc.

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GROWTH OF CHEMICAL KNOWLEDGE Evidence of the advances of chemistry in the 20th century can be seen in the exponential growth in the number of new synthetic substances. In the late 20th century, nearly 19 million substances were catalogued; in the early 19th century, only a few dozen were known.22 To understand the reasons for this dramatic increase, the state of chemistry in the early 20th century must be considered. With the industrial expansion of this period, new substances became necessary in order to meet technological demands, making chemistry seem like a passport

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dx.doi.org/10.1021/ed300098d | J. Chem. Educ. XXXX, XXX, XXX−XXX

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to a better future.23 Chemistry was definitely institutionalized in the form of industrial research and was focused on the creation and commercial production of new materials.24 By addressing the context for developing new molecules, one must point out the work of Thomas Midgley, Jr. A mechanical engineer by training, Midgley was a protagonist in the production of new compounds, such as tetraethyl lead and chlorofluorocarbons (CFCs), which were presented as solutions to pressing industrial problems. The way Midgley and colleagues arrived at these compounds points to intense reflection on the periodicity of elemental properties. In this work, by reviewing the development of these compounds, we intend to derive some implications for chemical education.

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additive to gasoline. Conducting more tests by synthesizing compounds with ethyl and phenyl groups, Midgley studied diethylselenide and diethyltelluride. Again, the issue of odor did not allow the use of these substances. Although these results were discouraging at first, Midgley started to consider the periodicity of properties of the elements as a guide for his trials after a suggestion of Robert E. Wilson from MIT.25 Thus, the periodic table became an aid in predicting the composition of new antiknock compounds to be tested. Following the table, the compounds that were tested after aniline contained elements from the nitrogen and carbon groups. Midgley and co-workers started to compare the antiknock power of similar compounds by means of graphs, such as the one reproduced in Figure 1 (from a paper published

DEVELOPMENT OF NEW MOLECULES

Tetraethyl Lead

The choice of tetraethyl lead resulted from new research about “knocking” in the fuel industry, which began in the late 1910s. As gasoline conventionally used at that time had a low octane rating, the fuel consumption of vehicles was higher because gasoline ignited easily. Thus, finding a way to improve the quality of gasoline (that is, to retard its ignition) was necessary. In this context, Midgley and colleagues, then working for Dayton Engineering Laboratories Company (Delco, later a subsidiary of General Motors) in Ohio, hypothesized that the octane rating of commercial gasoline could be increased upon the addition of an antiknock agent. This compound should be inexpensive and efficient while minimizing deleterious effects on the motor. As a starting point in the search for an antiknock agent, Midgley experimentally tested what has been called the “trailing arbutus theory”.25 According to this theory, one possible reason for the blooming of the trailing arbutus plant under snow was the fact that its red-backed leaves were capable of absorbing heat from the sun. Thus, Midgley thought that the addition of a red substance to gasoline might lead to the absorption of heat from the flame within the cylinder of the motor, causing gasoline to be slowly vaporized and preventing knocking. Following this rationale, iodine (which presents a reddish color in organic solution) had been tested, and its properties met Midgley’s expectations: it behaved as an antiknock compound. However, besides the toxicity of its fumes and the fact that the waste would corrode and clog the engine, the addition of iodine in gasoline would result in a considerable increase in its selling price. As a result, despite being an antiknock agent, iodine did not possess the appropriate properties to be added to fuels. However, these negative characteristics were not related to the “trailing arbutus theory”. In order to verify whether the antiknock properties were linked to the red color, Midgley and collaborators conducted tests with various compounds. Their experiments showed that ethyl iodide, which is colorless, was also an antiknock compound (with similar disadvantages to iodine), but red dyes diluted in kerosene did not prevent knocking. From these findings, Midgley began a process of searching for antiknock agents that had no iodine in their composition. After several random experiments based on trial and error, Midgley noted that aniline was an antiknock compound that was more effective than iodine. Because aniline is easily obtained from indigo, its cost of production would be considerably lower than that of iodine. Despite these apparent advantages, its ability to corrode metals and the unpleasant odor of the exhaustion gases prevented the use of aniline as an

Figure 1. Diagram used by Midgley to illustrate the antiknock effect of several compounds by comparing the influence of elements belonging to different groups of the periodic table attached to the ethyl chain. Reprinted from ref 27, p 244. Copyright 1937, American Chemical Society.

by Midgley in 1937). The knock-reduction ability of aniline was taken as a reference, and other compounds were compared to it. One can see that for each of the three groups of the periodic table (carbon, oxygen, and fluorine groups), the greater the atomic number of the element attached to the ethyl chain, the greater the knock-reduction property. Experiments showed that tin compounds, especially those with diethyltin, were excellent antiknock agents. These results suggested that a compound containing lead could be even better. In fact, the most satisfactory results were obtained with tetraethyl lead.26 As suggested by the graph, the effect of increasing atomic number on the antiknock property is dramatically higher in the carbon group compared with the other groups. The idealized antiknock compound had finally been found. On the change from trial and error to periodic table-oriented experiments, Midgley wrote (ref 27, p 242; emphasis added): B



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With these facts before us, we profitably abandoned the Edisonian method [i.e., trial and error] in favor of a correlational procedure based on the periodic table. What had seemed at times a hopeless quest, covering many years and costing a considerable amount of money, rapidly turned into a “fox hunt”. Predictions began fulfilling themselves instead of fizzling. Tetraethyl lead had been known by chemists since the 19th century. It was first obtained, in impure form, by the German chemist Carl Jacob Löwig (1803−1890) around 1853. George Bowdler Buckton (1818−1905) isolated and characterized it in 1859.28 However, it did not find any applications until the next century because of its great toxicity. Physicians from the United States were suspicious about the safety of tetraethyl lead as a gasoline additive, as problems caused by lead poisoning from inorganic lead were well-known.29 Midgley himself was warned about the “creeping poisonous effects” of tetraalkylleads by a letter forwarded to him by W. G. Whitman from MIT in 1922.30 Despite knowing these data, Midgley believed that there would be no real danger in the use of tetraethyl lead, for it should only be added to gasoline in small quantities. Thus, tetraethyl lead began to be produced on an industrial scale, and the first sale of a leaded gasoline to the public occurred in 1923.30 In the following year, General Motors (for which Midgley was already working) and Standard Oil formed a joint venture called the Ethyl Corporation to market the gasoline lead additive, and Midgley was assigned as general manager.31 As large scale production began, cases of poisoning and even deaths of workers started to occur at Deepwater, Dayton, and Bayway plants. In 1923, Midgley himself had developed symptoms of poisoning (digestive problems, subnormal body temperature, and reduced blood pressure) and left the laboratory to spend some weeks in Florida in recovery.30 Professionals from the United States Public Health Service (PHS) and other researchers from the medical arena warned about the risks of releasing lead into the environment by the cars’ exhaust. William Mansfield Clark, a laboratory director in the PHS, warned that “on busy thoroughfares it is highly probable that the lead oxide dust will remain in the lower (atmospheric) stratum”, which could constitute a “serious menace to the public health” (ref 32, p 18). Representatives of the tetraethyl lead industries, however, argued, “the average street will probably be so free from lead that it will be impossible to detect it or its absorption” (ref 32, p 19). Production of tetraethyl lead was interrupted in the United States from May 1925 to June 1926 while a committee appointed by the Surgeon General investigated the involved risks. The committee concluded that there was not enough evidence so far that tetraethyl lead was a menace to public health but that further studies should be conducted under the supervision of the Surgeon General. After the release of the committee’s report, leaded gasoline went back to the market. More strict safety measures were adopted by the industry, especially to prevent the exposure of workers to tetraethyl lead vapors. Further studies were funded by the Ethyl Corporation, which hired a multidisciplinary team headed by a physician and researcher from the University of Cincinnati, Robert Kehoe. Not surprisingly, Kehoe’s team results suggested that available data did not support the conclusion that the lead dispersed by the exhaust of cars was a danger to public health. These findings were decisive for the continued use of tetraethyl lead as a

gasoline additive in the United States and around the world for the next decades. An Ethyl Corporation report, dated 1963, stated that 98% of the gasoline sold in the United States contained antiknock lead compounds.30 The ban of tetraethyl lead in the United States began only in the 1970s, as a consequence of a federal act for the control of atmospheric pollutants.33 Chlorofluorocarbons

By the late 1920s, Midgley already had a distinguished career. He was vice president of Ethyl Corporation and a consultant to General Motors. Considered a great specialist in solving problems in the chemical industry, Midgley received another complex task: finding a new fluid to be used in the refrigeration industry. At that time, conventional fluids used in refrigerators, such as ammonia, sulfur dioxide, or chloromethane, posed risks of explosions and poisonings, which limited the use of refrigeration appliances, especially in places with many people around. For example, in 1929, a series of deaths in Chicago were caused by chloromethane leaks from refrigeration devices.34 Another shortcoming of using toxic and flammable refrigerant fluids was the impossibility of equipping cars with air conditioning systems, an issue that probably was among the concerns of the automotive industry. Soon, a demand arose for a refrigerant that was simultaneously nontoxic, nonflammable, and inexpensive. In order to make it suitable for industrial applications, the desired fluid should liquefy easily with increasing pressure without requiring the use of very low temperatures and absorb energy from the environment to return to its gaseous state. Table 1, reproduced from an article Table 1. Properties of Some Common Refrigerants Used As Refrigerating Agents Prior to CFCsa engineering properties

refrigerants air carbon dioxide water ammonia

does not liquefy excessive vapor pressure excessive vacuum ok

sulfur dioxide methyl chloride methyl bromide butane

ok

a

ok vacuum ok

inflammability

toxicity

ok ok

ok ok

ok very slightly inflammable ok

ok toxic; gives warning toxic; gives warning toxic; gives warning toxic; gives warning ok

slightly inflammable slightly inflammable very inflammable

ample ample no no

Adapted from the table originally published in ref 35, p 542.

written by Midgley and Albert L. Henne35 in 1930, provides a comparison of relevant properties of substances that were used as fluids in refrigerators. By carefully analyzing each of the refrigerants in Table 1, it is clear that none of them fully satisfied the three properties mentioned above: engineering properties (stability, noncorrosiveness, and suitable vapor pressure), low flammability, and minimal toxicity. Willing to tackle this problem, Midgley, Henne (a specialist in organochlorides), and their co-workers embarked on the search for new fluids for use in the refrigeration industry. Observing the periodic table according to the organization of Langmuir (Figure 2), Midgley started to speculate on the properties of the elements in order to determine what kind of compound could have the set of desired properties for a C



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Figure 2. Periodic table based on Langmuir’s theory of atomic structure. Reprinted from ref 27, p 243. Copyright 1937, American Chemical Society.

refrigerant fluid. In the following quotation, Midgley summarized their approach to the problem (ref 27, pp 242 and 244): [I]n Figure 2, the elements on the right-hand side are the only ones which make compounds sufficiently volatile for the purpose in hand. (...) Volatile compounds of boron, silicon, phosphorus, arsenic, antimony, bismuth, selenium, tellurium, and iodine are all too unstable and toxic to consider. The inert gases are too low in boiling point. Now look over the remaining elements. (...) Flammability decreases from left [carbon] to right [fluorine]. Toxicity (in general) decreases from the heavy elements at the bottom to the lighter elements at the top. These two desiderata focus on fluorine. Such deduction seemed surprising because the simple substance fluorine was known to be highly toxic. Thus, Midgley and Henne started to look for a fluorine-containing compound with the desired properties.27 From the physicochemical properties of methane (CH4), carbon tetrafluoride (CF4), carbon tetrachloride (CCl4), and other organochlorides, Midgley and Henne prepared diagrams relating the boiling points to the stability, toxicity, and flammability of these compounds and of various organic halides. One difficulty encountered in this journey was a disagreement about the boiling point of carbon tetrafluoride; the duo concluded that the correct value was −128 °C, as opposed to −15 °C; this misconception was believed until the late 1930s. In Figure 3 (also reproduced from ref 35), it is possible to observe that the boiling points of CFCl3 and CF2Cl2 are in the range between −30 and +30 °C (carbon and hydrogen atoms were omitted from chemical formulas represented in Figure 3). Together with low flammability and toxicity, this set of properties made CFCl3 and CF2Cl2 suitable for use in refrigerant devices. The chemical equation below illustrates the method used by Midgley and colleagues to prepare chlorofluorocarbons (CFCs). In the case of CCl2F2, they reacted CCl4 and SbF3:37 SbCl5

3CCl4 + 2SbF3 ⎯⎯⎯⎯→ 3CCl 2F2 + 2SbCl3

CFCs and tetraethyl lead were produced on a large scale at a time when environmental problems arising from their use were not imaginable or fully understood. When the scientific and sociohistorical consequences of the use of these products is considered, the cases of the development of tetraethyl lead and CFCs reveal a rich potential for discussions in the context of chemical education.

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MIDGLEY’S COMPOUNDS AS A CASE STUDY FOR CHEMICAL EDUCATION

Results of Adopting a Chemical Approach

One of the most intriguing aspects of this case study is the way that Midgley, an engineer, changed his approach to research new compounds. Initially, he was guided by an approach that had little to do with modern chemistry. His reasoning was by analogy: if the red color in the trailing arbutus plant allowed for the retention of heat in cold weather, then perhaps red dyes could also increase the octane rating of gasoline. This reasoning relied on a theoretical “principle” responsible for the red color in the trailing arbutus plant and other materials that also caused heat retention. Midgley experimented with many red-colored substances, guided only by this idea, which we now could consider quasi-alchemical. However, his approach changed dramatically when Midgley turned to the periodic table and used it to predict new compounds with the desired properties. The relevance of the periodic table as a working tool for the modern chemist must not be underestimated. As highlighted by Scerri,10 “The periodic table of the elements is one of the most powerful icons in science: a single document that captures the essence of chemistry in an elegant pattern.” Literature shows that the periodic table of elements has been presented in many different ways.10,36 According to Nelson,37 the choice of each table depends on the subject being taught. For example, if the periodic table is needed to introduce middle school students to simple concepts, a simple version can be prioritized. The presentation of the periodic table organized by the Langmuir system, though, requires that students have some knowledge of structural chemistry. Therefore, the discussion of this specific detail of the case study could be useful in more advanced levels of education, for example, in teachers’ continuing education and for undergraduate or graduate students who are interested in chemical education. Other relevant aspects of Midgley’s experiences concerning the nature of science that emerge from this case study may be discussed at different education levels. Of course, the depth of the discussion will depend on the education level and on the

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Testing the toxicity of CCl2F2 in guinea pigs, Midgley did not notice any detrimental biological effects (Table 2). The trade names of CFCs have been based on the relationship between the number of carbon and fluorine atoms in the molecules (e.g., CFCl3 was known as CFC-11, and CF2Cl2 was named CFC12). D



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scientific contents, then the work with this case study in the classroom may be useful. Focusing on the development of tetraethyl lead and CFCs, we can discuss the following questions, among other related topics: 1. Scientific knowledge may not be created as an end in itself: it reflects the search for solutions to problems, be they intellectual or (as in this case) of a practical nature. When acquainted with this idea, students will be more likely to ascribe significance to chemical concepts instead of asking questions such as “Why did someone invent the periodic table?” or “Why do I have to study organic chemistry?” 2. Science is not done in a linear and cumulative manner; it may take unexpected directions. In this case, although the toxicity of lead compounds was known, the economic interests appear to have overpowered health-related studies aimed at minimizing such risks. 3. An alternative theoretical perspective can be very useful for the development of a field of science or technology. Midgley was educated as a mechanical engineer, and his first attempts to produce an antiknock gasoline displayed his poor knowledge of modern chemistry. However, by understanding the usefulness of the periodic table, his approach to the issue became much more effective. 4. One of the signature aspects of chemistry is the production of new substances and materials that do not exist in nature. This activity can be inherently dangerous, requiring from chemists a great deal of professional responsibility.38 This case study shows three dimensions of chemical risk. Tetraethyl lead posed a risk to workers directly exposed to it during its production (individual risk) and to regions where vehicular traffic caused the dispersion of lead compounds (local environmental risk). CFCs, in turn, remained intact in the lower atmosphere. However, scientists only realized after decades had passed that CFC caused the destruction of the ozone layer after diffusing into the stratosphere, a process that if not interrupted could endanger all life forms on the planet (global environmental risk).39 The introduction of such issues in chemistry classes may help students to develop a more complex view about science, beyond the mere and strictly inductive empiricism and toward a more rationalist approach.

Figure 3. Chart comparing the physicochemical properties of different CFCs. Carbon and hydrogen atoms are not represented in the formulas. Reprinted from ref 35, p 543. Copyright 1930, American Chemical Society.

Topics for Class Discussion

One possible way to work with pre-service or in-service teachers is to present this case study as a text to be read and discussed in groups. To guide the discussion, some questions may be proposed in printed form. The aim of such questions should be to foster critical thinking on the issues raised by the text. Here, we suggest some questions that could be discussed.

educational aims. If a teacher believes that among his or her goals is helping students understand the process of construction of science and its relations to society, and not only to learn

Table 2. Comparative Toxicity of Dichlorodifluoromethane and Common Refrigerants Used To Manufacture Refrigeratorsa toxicity concentrations, % by volume in air

a

refrigerant gas

kills animals in a very short time

dangerous to life in 30−60 min.

maximum for several hours without danger to life

ammonia methyl chloride carbon dioxide dichlorodifluoromethane

0.3−1.0 15−30 30 not attainable

0.25−0.45 2−4 6−8 80

0.01 0.05−0.1 2−3 40

Adapted from the table originally published in ref 35, p 544. E



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· Compare the ways Midgley conducted research before and after he discovered the usefulness of the periodic table. In your opinion, what is the role of the periodic table in the professional activities of chemists? · Do you think the fact that Dr. Robert Kehoe was hired by Ethyl Corporation may have influenced his opinion on the risks posed by tetraethyl lead? Explain your opinion. · Ethyl Corporation was interested in selling tetraethyl lead and conducted scientific studies that pointed to the safety in the use of this chemical. In your opinion, must there be some kind of regulation for the manufacture and sale of innovations produced by the chemical industry? If no, why? If yes, how could this regulation be done? Explain. · At the time Midgley and Henne concluded that CFCs would be the most suitable fluids for the refrigeration industry, they did not know that these compounds represented a risk to the ozone layer. Do you think Midgley and Henne were reckless? Is it possible to predict all risks posed by new substances with practical applications synthesized by chemists? How should technological innovations of creating new substances be simultaneously managed with necessary precautions to prevent human exposure and chemical risks to the environment? Different opinions should arise, and the discussion participants would not necessarily reach a consensus at the end of the discussions. Most important for teacher education in this case is the very process of construction and comparison of arguments and the realization that the divergence of views can be healthy. Thus, this type of activity could help change an attitude that Höttecke and Silva2 described as part of the culture of science educators and as one of the obstacles to implement the history and philosophy of science in the classroom: that science teachers usually lack essential teaching skills for guiding activities such as discussions and negotiations of different opinions among students.

ACKNOWLEDGMENTS The authors thank Brazilian agencies Conselho Nacional de ́ Desenvolvimento Cientifico e Tecnológico and Fundaçaõ de Amparo à Pesquisa do Estado de São Paulo for financial support.

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REFERENCES

(1) Matthews, M. R. Science Teaching: The Role of History and Philosophy of Science; Routledge: New York, 1994. (2) Höttecke, D.; Silva, C. C. Sci. & Educ. 2011, 20, 293−316. (3) Allchin, D. Sci. & Educ. 2004, 13, 179−195. (4) Martins, R. A. Introduçaõ : A História das Ciências e Seus Usos na ́ Educaçaõ . In Estudos de História e Filosofia das Ciências: Subsidios para ́ Sua Aplicaçaõ no Ensino; Silva, C. C., Ed.; Editora Livraria da Fisica: São Paulo, 2006; p 17−30. (5) Irwin, A. Sci. Educ. 2000, 84, 5−26. (6) Metz, D.; Klassen, S.; McMillan, B. A.; Clough, M.; Olson, J. Sci. & Educ. 2007, 16, 313−334. (7) Viana, H. E. B.; Porto, P. A. Sci. & Educ. 2010, 19, 75−90. (8) Souza, K. A. F. D.; Porto, P. A. J. Chem. Educ. 2012, 89, 58−63. (9) Stinner, A.; McMillan, B. A.; Metz, D.; Jilek, J. M.; Klassen, S. Sci. & Educ. 2003, 12, 617−643. (10) Scerri, E. R.; The Periodic Table: Its History and Its Significance; Oxford University Press: New York, 2007. (11) Brito, A.; Rodriguez, M. A.; Niaz, M. J. Res. Sci. Teach. 2005, 42 (1), 84−111. (12) Diener, L.; Moore, J. W. Sci. Teach. 2011, 78 (5), 40−43. (13) Lemes, M. R.; Dal Pino, A. J. Chem. Educ. 2011, 88 (11), 1511− 1514. (14) Winter, M. J. J. Chem. Educ. 2011, 88 (11), 1507−1510. (15) Wiediger, S. D. J. Chem. Educ. 2009, 86 (10), 1212−1215. (16) Chen, D. Z. J. Chem. Educ. 2010, 87 (4), 433−434. (17) Coppola, B. P.; Smith, D. H. J. Chem. Educ. 1996, 73 (1), 33− 34. (18) Kovac, J. Found. Chem. 2000, 2, 207−219. (19) Jacob, C.; Walters, A. Hyle: Int. J. Phil. Chem. 2005, 11 (2), 147−166. (20) Eriksen, K. K. Hyle: Int. J. Phil. Chem. 2002, 8 (1), 35−48. (21) Sjöström, J. Hyle: Int. J. Phil. Chem. 2007, 13 (2), 83−97. ́ 1999, 10 (2), 92−101. (22) Schummer, J. Educ. Quim. (23) Midgley, T., Jr. Ind. Eng. Chem. 1935, 27 (5), 494−498. (24) Mauskopf, S. H. Introduction. In Chemical Sciences in the Modern World; Mauskopf, S. H., Ed.; University of Pennsylvania Press: Philadelphia, 1993; p xi−xxii. (25) McGrayne, S. B. Prometheans in the Lab: Chemistry and the Making of the Modern World; McGraw-Hill: New York, 2002. (26) Garrett, A. B. J. Chem. Educ. 1962, 39 (8), 414−415. (27) Midgley, T., Jr. Ind. Eng. Chem. 1937, 29 (2), 241−244. (28) Seyferth, D. Organometallics 2003, 22, 2346−2357. (29) Needleman, H. Annu. Rev. Med. 2004, 55, 209−222. (30) Seyferth, D. Organometallics 2003, 22 (24), 5154−5178. (31) Loeb, A. P. Bus. Econ. Hist. 1995, 24 (1), 72−87. (32) Rosner, D.; Markowitz, G. Am. J. Public Health 1985, 75, 344− 352. Quoted in Nriagu, J. O. Sci. Total Environ. 1990, 92, 13−28. (33) The United States Environmental Protection Agency, a federal agency created by President Richard Nixon in 1970, lobbied strongly against the manufacture of tetraethyl lead from its foundation. See Seyferth, ref 30 (34) Giunta reports that accounts that the development of new refrigerants was triggered by a disastrous accident at a Cleveland hospital in 1929 were inaccurate, as were some other anecdotes frequently associated with Midgley’s life and work. See Giunta, C. Bull. Hist. Chem. 2006, 31 (2), 66−74. (35) Midgley, T., Jr.; Henne, A. L. Ind. Eng. Chem. 1930, 22 (5), 542−545. (36) Monaghan, P. K.; Coyne, M. Educ. Chem. (London, U. K.) 1988, 25, 139−141. (37) Nelson, P. G. Educ. Chem. (London, U. K.) 1988, 25, 185−187.

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CONCLUDING REMARKS In the context of teacher education in chemistry, this case study investigating the development of tetraethyl lead and CFCs can serve to promote different types of reflections. One point of reflection shows technological problems being solved on the basis of knowledge of the periodic properties of chemical elements. Another set of reflections centers on important aspects of the nature of scientific knowledge, including the fact that science does not constitute a set of absolute truths and that ethical principles are primarily involved in the activity of chemical synthesis, especially at the industrial scale. Thus, this case study can aid chemistry teachers in critical and reflective thinking, as recommended by current curricular guidelines.

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AUTHOR INFORMATION

Corresponding Author

*P. A. Porto. E-mail: [email protected]. Notes

The authors declare no competing financial interest. F



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(38) Schummer, J. The Philosophy of Chemistry. In Philosophies of the Sciences; Allhoff, F., Ed.; Blackwell-Wiley: Chichester, U. K., 2010; p 163−183. (39) Viana, H. E. B.; Corio, P.; Porto, P. A. Número Extra VIII Congreso Internacional sobre Investigación en Didáctica de las Ciencias, Barcelona. Enseñanza de las Ciencias 2009, 1816−1819.

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Thomas Midgley, Jr., and the Development of New Substances: A

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