Instruments and Theory
The influence of experimental physics on chemical theory was still negligible in the middle of the century. Although interest in Newtonian ideas about affinity then began to increase, and although affinity was supposed to be a distance force, the tables remained descriptions of empirical facts, in practice irrelevant to any theory of affinity. This generalization holds for the work of the thoroughgoing Newtonian Etienne François Geoffroy and also for Bergman, who brought the affinity tables to their fullest form.[57] Also, the Newtonian concept of the ether did not attract attention during the heyday of phlogiston and affinity studies. It later influenced Lavoisier.[58]
The influence of physics on chemistry was most evident on the continent in France, which, perhaps not coincidentally, had a relatively weak tradition in mining.[59] In Germany and in Sweden, chemists took less interest in physics because of the difficulties of applying it to mineralogy and because of the tendency of Stahl and his followers to keep Newtonian mechanics away from practical chemical work. Chemists who did show interest in physics in the last decades of the 18th century typically had some attachment to the universities. That in any case was true of Sweden.[60]
Relations between mathematics and chemistry were strained by the inability of the one to calculate anything of interest for the other. This was especially true in atomic theory. As Joseph Black put it, the assumption that a certain attractive force existed between certain atoms was void, since "all the mathematicians of Europe are not
[57] For Geoffroy, see I.B. Cohen in Melanges Alexandre Koyré, 1 , 102; for Bergman, A. Duncan, "Introduction," in Torbern Bergman, A dissertation on elective attractions, 2d ed. (London: Cass, 1970).
[58] Evan M. Melhado, "Oxygen, phlogiston, and caloric: The case of Guyton," Historical studies in the physical sciences, 13 (1983), 311–-34, esp. 311–20.
[59] Henry Guerlac, "Some antecedents of the Chemical Revolution," Chymia, 5 (1959), 73–112; also in Essays , 340–74.
[60] Karl Hufbauer, The formation of the German chemical community , 97; A. Lundgren, "The new chemistry in Sweden: The debate that wasn't," Osiris, 4 (1988), 146–68.
qualified to explain a single combination by these means."[61] Macquer, though appreciative of Newtonian methods, thought that some mathematics was needed to formulate a general theory of chemistry; "but that [he said] does not fall into our line of work." As a pharmacist he recognized the complicated reality of the chemist: "Perhaps chemistry is not yet sufficiently advanced to be made the subject of calculation, perhaps it will never be [since] the problems that it will present mathematicians might be so complicated that they would be beyond all human effort."[62] Bergman, who was close to Pierre-Joseph Macquer and Guyton de Morveau, had a thorough knowledge of physics, admired Newtonian methods, and was capable in mathematics. None of these tools seemed useful for the study of the atom. For Bergman, empirical knowledge of atoms was itself impossible; certainly they could not be studied quantitatively.[63]
What chemists did take from experimental physics was an instrumentalist attitude toward theories. William Cullen and Joseph Black, following one methodological approach inherited from Newton, insisted that empirical knowledge and theoretical explanations should be kept separate.[64] The first part of Black's classical treatise, Experiments on magnesia alba (1750), is given over to experiments; the second, to their interpretation and theoretical explanation.[65] The instrumentalist approach fit well with a new view of theories during the late 18th century. English chemists wrote about the caloric
[61] Black, Chemical lectures, 1 , 283. Although it is difficult to separate Robison's views from Black's, at issue here is the attitude itself.
[62] Melhado, "Oxygen, phlogiston, and caloric," 320; J.P. Macquer, Dictionaire de chymie , 4 vols., 2d ed. (Paris: P. Fr. Didot, 1778), 3 , 88, s.v. "pesanteur." Cf. Thackray, Atoms and powers , 208f.
[63] For Bergman's Newtonianism, see "Introduction," in his A dissertation on elective attractions , translated from Latin (London: J. Murray and Charles Elliot, 1785); for the impossibility to measure atoms, see his "Företal," in H.T. Scheffer, Chemiske föreläsningar (Uppsala: M. Swederi, 1775), 6.
[64] Stephen Hales, Statical essays: Containing vegetable statics , 3d ed. (London: Innys and Manby, 1738), 170–2; A.L. Donovan, "Pneumatic chemistry and Newtonian natural philosophy in the eighteenth century. William Cullen and Joseph Black," Isis, 67 (1976), 217–28, and Philosophical chemistry in the Scottish Enlightenment (Edinburgh: Edinburgh University Press, 1975), 24–5.
[65] See Donovan, Philosophical chemistry , for a fuller analysis. Priestley does not break the general scheme: cf. S. Schaffer, "Priestley's questions: An historiographic study," History of science, 12 (1984), 151–83.
theory of heat in an instrumentalist way and did not commit themselves about its absolute truth.[66]
Instrumentalism triumphed in chemistry with Lavoisier's definition of an element.[67] It was perhaps his most important contribution to a new theoretical role for numbers in chemistry. The definition of a chemical element as the simplest substance available in the laboratory ignored philosophical questions concerning the structure of matter and denied elementary status to the old elements and principles. Lavoisier's definition turned the concept "element" into empirical operations independent of any hypothesis about the structure of matter; at the same time he made the definition the starting point for the construction of theories.
Lavoisier's view of chemical elements represented a break from the earlier concept of chemical facts as so many benchmarks in the search for absolute truth.[68] Lavoisier's definition augmented by the atomic theory, gave numbers a new function in chemistry. This theory can be regarded as a combination of definite chemical proportions, derived from practical chemistry, with the instrumentalist notion of a simple body, derived from experimental physics. Dalton's atomic theory used numbers to express its central concept—atomic weight. With the help of Dalton's rules of simplest combination and the assumption of definite proportions, the different weights could be interrelated. The balance thereby acquired a definitive role in the construction of chemical theory.
Although the atomic theory gave to chemistry numbers invested with theoretical significance, it did not provide generalized laws in mathematical form. The study of discrete atomic weights thus made it possible to combine theory and practice in a quantitative way without commitment to the existence of atoms. The atomic theory
[66] Robert Fox, "Dalton's caloric theory," in D.S.L. Cardwell, ed., John Dalton and the progress of science (Manchester: Manchester University Press, 1968), on 92; Russell McCormmach, "Henry Cavendish on the theory of heat," Isis, 79 (1988), 37–67; Hankins, 107; Christie, "Ether," 101–3.
[67] Guerlac, in "Quantification in chemistry," considers quantitative descriptions of individual facts an essential part of quantification in chemistry, but does not discuss its significance for chemical theories.
[68] See Hufbauer, The formation of the German chemical community , 8–10.
eventually overcame philosophical opposition by its success in explaining experimental facts and by distancing itself from physical atomic theory.[69]