Why Distillation?

Given the pervasive skepticism about distillation by fire, why did academicians not discard it in favor of alternative methods? They could have

tested the natural juices of plants with color reactors, observed the crystals formed by plant juices, studied vegetable dyes, or used solvent analysis.^[37] Duclos,  Dodart , and Perrault had discussed the first three of these techniques, while Borelly and Duclos promoted extraction by solvents. But two academicians — Bourdelin and  Dodart  — saw to it that the Academy continued distilling plants, in spite of shortcomings and alternatives.

Bourdelin's influence is surprising, because his role in the institution was so circumscribed. Of all the academicians involved with the natural history of plants only the two Marchants had as little power as Bourdelin. After the 1660s, his contributions to meetings were confined almost entirely to reporting on his distillations. His early papers on chemical research were ignored by the Academy, and his notebooks record experiments made according to the instructions of Duclos,  Dodart , Borelly, and others. Yet if he could not initiate research, he could veto it, and he was markedly reluctant throughout the century to use any method of analysis other than distillation.  Dodart  suggested that soils be lixiviated instead of distilled, but Bourdelin continued distilling them, and when Borelly criticized him for this, Bourdelin stopped analyzing soils altogether. Both Duclos and Borelly wanted to use solvents, but again Bourdelin resisted. Since no other academician was willing to devote all his time to analyzing plants, animals, and minerals chemically, Bourdelin was able by default to perfect his chosen technique.

 Dodart , too, favored distillation, and as director of the natural history his opinion carried weight. Distillation seemed appropriate for two reasons: it was a universal method which permitted comparison of all plants according to a single standard,^[38] and it promised insights into how food nourished and medicines cured the body. Bourdelin's analyses hence seemed promising to  Dodart's  own research, and because the natural history could not proceed without  Dodart  and Bourdelin, their advocacy was decisive.

The most touted but controversial alternative to distillation was solvent analysis. Duclos had originally laid out a narrow sphere for solvent analysis in 1668. Distillation by fire, he argued, was best for separating the chemical constituents of most substances. The exceptions were "fixed substances and those which cannot be burned." These required "dissolving menstruums which break up the mass and render the constituent parts separable." Any substance that a fire could not distill required analysis with solvents. Pure earths, metals, glass, chalk, and minerals were all "fixed" in varying degrees; solvents offered the only hope of analyzing them.^[39]

Duclos's interest in the subject had Paracelsian origins, and he supplied the recipe for what he claimed was the true alkahest or universal solvent.^[40]

Solvent analysis was one of the issues that alienated Duclos from  Dodart . The two argued about solvents in the early 1670s. When  Dodart  came across Duclos's recipe for the universal solvent, he mocked it as worthless for analyzing plants. In January 1675 he derisively asked the chemist to consider whether the solvent might shed light on the "marvelous effects" attributed to plants. Duclos's recipe,  Dodart  maintained, was as enigmatic as those of Paracelsus, Helmont, or Deiconti. Even if it was possible to make a universal solvent, it "would not help us understand the nature of plants any better, because each plant would be reduced by the operation of these solvents to a state" in which it would be indistinguishable from any other plant so treated. He derided universal solvents as being as useless as the theories of signatures and temperaments.^[41]

This exchange occurred after Duclos modified his view. He now believed that solvent analysis offered

a much better method than that of the fire since a solvent does not alter things, but leaves them as they are and reduces them to their constituent principles while preserving their virtues and their specific properties, something the fire cannot do.^[42]

Furious at  Dodart's  attack, Duclos criticized "the author of the project who always speaks in the name of the Company without being so charged" for having characterized "universal solvents as vain and useless."  Dodart  embarrassed the Academy, he claimed, by representing it as mistrustful of methods recommended by "famous chemists."^[43] Ironically, it was Duclos who discomfited his colleagues by publishing his alchemical Dissertation sur les principes des mixtes in Amsterdam after a committee of academicians had advised against its publication.^[44]

Duclos's alchemical interests made him an unconvincing proponent of solvent analysis. Borelly, however, was untainted by Paracelsianism and he too favored solvents over distillation. Like Duclos he collected reports about their use, and the year after Duclos died Borelly proposed that all kinds of solvents be prepared. Perhaps he hoped to convince his wary colleagues that solvent analysis did not necessarily depend on alchemical precepts.^[45] But his death in 1689 left the field to Bourdelin and  Dodart .

Why did the Academy continue to analyze plants? Members recognized the shortcomings of distillation and its results baffled them, but they mistrusted solution analysis more. Why did they persist? The answer does

not lie merely in the persuasiveness of the method's proponents, who brushed aside problems as due to imprecise observations. Rather, the steadfast analysis of plants by academicians in the face of apparent failure results from the high premium they placed on the basic goals of chemical analysis.