Pneumatic chemistry

The stage was now set for a critical examination of phlogiston theory and the birth of modern chemistry. By the mid- 

Joseph Black (1728-1799) conducted an important series of experiments during work on his doctoral dissertation in medicine. Black was searching for a material to dissolve kidney stones. He chose magnesia alba (magnesium carbonate), but 

Black decided that the gas given off in the reaction between magnesia alba and acid was similar to one described by van Hel-mont. He coined the term fixed air to indicate that this gas was fixed or trapped in magnesia alba. Black also recognized that fixed air was the same gas produced in respiration, combustion, and fermentation. Today, we know Black s fixed air was car- 

Joseph Black, upon completion of his study on magnesia alba, received his medical degree. He published very little after this study. Black taught at universities in Glasgow and Edinburgh, and continued to do solid research, which he presented in his lectures. One area in which he did important work was heat and the latent heat of steam. His work in this area inspired one of his students James Watt to apply Black s ideas in making improvements to the steam engine. 

Similar to Black, Daniel Rutherford (1749-1819) studied gases for his medical degree dissertation. Rutherford found that common air contained a part that supported respiration and a part that did not. Initially, Rutherford assumed the part that did not support respiration was contaminated by fixed air. Rutherford experimented and removed the fixed air, and he discovered the uncontaminated air still did not support life or combustion. Rutherford assumed the gas he had isolated was ordinary air saturated with phlogiston hence, it was phlogisticated air, which he referred to as noxious air. What Rutherford had isolated was nitrogen, and he is given credit for its discovery. 

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Joseph Priestley was born in Fieldhead, a tiny hamlet near Leeds, on March 13 (old style), 1733, and was therefore about one and one-half years older than that other great pioneer in pneumatic chemistry, Mr. Henry Cavendish. Although Priestley and Cavendish had similar scientific interests, their lives and personalities offered the greatest possible contrast. Since Priestley s mother died when he was only six years old. he was entrusted to the care of an aunt, Mrs. Keighley, of whom he afterward said that she knew no other use of wealth, or of talents of any kind, than to do good (21). 

Plasma state of matter in which atoms or molecules have been ionized to form positive ions and electrons Plasmolysis condition that results when cells absorb water and rupture Pneumatic Chemistry study of gases and air, important in the development of modern chemistry... 

Perhaps because of the mystical religious context in which he embedded his descriptions of gases, his discoveries made little contribution to the later development of pneumatic chemistry. His term gas became standard usage only late in the next century. 

Conceptually, the most important point here is the clear distinction Rouelle made between the chemical and physical aspects of behavior. Historically, the most important point was the preparation this view made for the return of air, or gases, to chemical attention. As we shall see in Chapter Nine, the focused attention on air made possible the extension of the phlo-dgistic doctrine to pneumatic chemistry, to the increased benefit of both. 

Another very important point for the compositional story is Blacks recognition that fixed air plays the part of an acid in saturating the caustic alkali, and thus pneumatic chemistry joins with the major body of empirical chemical knowledge, that of neutral salts ... 

Pneumatic chemistry expanded beyond the fixed air of Black when the Englishman Fienry Cavendish (1731-1810) published his Three Papers,... 

Lavoisier began his scientific career just about the time that pneumatic chemistry became widely recognized as important, so it is not surprising that he saw in this a great opportunity. Lavoisier had attended the chemistry lectures of Rouelle, and there witnessed the phenomena of aerial fixation and liberation, especially in effervescence. Before he was thirty years old, he initiated a systematic investigation of the manner in which gases were fixed into and liberated from solid bodies, the importance of which... 

Robert Siegfried, Lavoisier s View of the Gaseous State and its Early Application to Pneumatic Chemistry, Isis 63 (1972) 59-78 at p. 62. See also Jerry Gough, The Origins of Lavoisier s Theory of the Gaseous State, in The Analytic Sprint Essays in the History of Science in Honor of Henry Guerlac, ed. Harry Woolf (Ithaca, New York Cornell University Press, 1981). 

Lavoisier s chemistry was now essentially complete, and we can turn to a brief account of the development of a systematic chemical nomenclature through which Lavoisier s pneumatic chemistry became joined with the mainstream of empirical knowledge of the neutral salts. 

The contribution of Bergman to the knowledge of carbonic acid or aerial acid will be alluded to in connection with the development of Pneumatic Chemistry, and his extensive work on Chemical Affinity will be referred to in connection with the history of early ideas on that subject. 

The researches which distinguish Black, Cavendish, and Priestley as chemists, were almost entirely on the preparation, properties, and reactions of gases. On account of the importance of the chemistry of gases or pneumatic chemistry in the development of chemical science, it will be worth while to follow chronologically the work and ideas of chemists on this subject, the researches and views of Van Hclmont, Rey, Boyle, Hook, and Mayow having already been considered. 

No Englishman took a more prominent part in the discoveries in pneumatic chemistry than did Joseph Priestley. Without training in science, unfamiliar with the previous work of chemists in general, Priestley took up the study of chemistry as an amateur, but with great enthusiasm, a decided talent for experimental devices, and... 

The first period in the development of combustion science was a period of determination of the basic chemical facts to this period belong the refutation of the phlogiston theory and the discovery of oxygen, the discovery and study of the properties of carbon monoxide and carbon dioxide, and the so-called pneumatic chemistry —the investigation of various gases and determination of the stoichiometric laws (1650-1820). 

On De Luc s reliance on Scottish pneumatic chemistry and the growing hegemony of chemistry in meteorology at this time see V. Jankovic, Reading the Skies A Cultural History of English Weather, 1650-1820 (Manchester Manchester University Press, 2000), pp. 151—4. That reliance is treated in more detail in T. S. Feldmann, The History of Meteorology, 1750—1800 A Study in the Quantification of Experimental Physics , Unpublished PhD Dissertation, University of California, Berkeley, 1983. 

Kirwan s measurement of affinities, which won him the Copley Medal of the Royal Society, was directly stimulated by Guyton s work. " The three papers he presented to the Royal Society contained a number of innovations that lasting effects on European chemistry. Though Kirwan usually emerges in the historiography of the Chemical Revolution as a loser who supported the phlogiston theory, his focus on the saturation capacity of acids and bases as the true measure of affinities opened a new frontier of analytic chemistry which developed into nineteenth-century stoichiometry. He also tapped the true revolutionary potential of pneumatic chemistry by enlisting marine acid air as the... 

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