Reaping the rewards of a century

The coherent and systematic method for a new chemical nomenclature, to which Guyton de Morveau, Lavoisier, BerthoUet, and Fourcroy aspired with their 1787 proposal, presupposed an equally coherent and systematic classification of pure chemical substances. Yet the authors of the Methode could not simply resort to an established classification suitable for their purpose. First, their project was inextricably linked with Lavoisier s new chemistry. The nomenclatural proposal of the four authors was constructed in the framework of Lavoisier s anti-phlogistic chemical system and thus presupposed a classification in conformity with this new system. Second, as we have shown, there existed in the framework of the traditional phlogistic system many partial classifications of pure chemical substances, both exphcit and implicit, as well as a few comprehensive classifications of the entire mineral kingdom. But there was no elaborated classificatory system devoted precisely to the realm of pure chemical substances. Therefore, even if the authors of the Methode had modestly confined themselves to proposing only a nomenclature in accordance with the phlogistic chemical system, this goal, too, would have required a lot of classificatory work. 

However, as our historical survey showed, by no means did they have to start from zero, but were able to build on the classificatory distinctions and distributions of both their predecessors and their contemporaries. And this was true not only for single groups of particular substances or subdivisions of certain taxonomic units. Rather, essential features of their classification of pure chemical substances had been developed in the course of the eighteenth century. 

However, the classification of the Methode was not only indebted to but also distinguished from the former affinity tables and other classificatory efforts of the eighteenth century. The first distinguishing feature that must be emphasized is its comprehensiveness. The Tableau was the first relatively comprehensive and explicit 

Less obvious than these extensions may be the Methode s transgression of a fundamental limitation of the classifications of the affinity tables. The main purpose of these tables was the rendering of replacement reactions. They were thus confined to those pure chemical substances actually involved in or resulting from such kind of reactions. A particularly drastic result of this confinement was the fact that metal calces did not appear among the substances involved in reactions in the dry way, since calcination by combustion was not regarded as replacement reaction. The two new classes of certain compounds of metal oxides and compounds of sulfur, carbon, and phosphorus (field IV/c and Vl/b) can be taken as another case in point, one which 

When referring to the Tableau s fields—field 1/a, etc.-particularly figure 5.4. 

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