Classificatory structure

Turning now to the columns and their classes, the first feature of the classificatory structure that must be stressed is the exceptional position of column I. Whereas the five other columns, without exception, contain the classes of substances regarded by the authors of the Methode as compounds, column I comprises only classes of substances that these men took to be simple substances—that is, non-compounds. 

Figure 5.4 Classificatory structure of the Tableau de la nomenclature chimique.

Among the graphical means by which the table represents the taxonomic units and their relations, there is one by which it transgresses the ordinary classificatory structure of hierarchically nested taxonomic units. The table arranges the taxonomic units in the manner of a matrix. Because of this layout, all of the genera and species are related in a twofold way to other units of the same rank. Vertically, they are related to those taxonomic units that are of the same class—either the class of simple substances (column I) or one of the five classes of compounds (colunms II-VI). Horizontally, the species are related to their compounds when they are simple substances.Or, if they are compound substances, they are related to one of their components and at the same time to other compounds of this component. Thus the Tableau contains two different, but coordinated classificatory systems vertically, a system that distributes genera of substances into either the class of simple substances or into one of the five classes of compounds and horizontally, one that orders compounds according to one simple substance that these compounds have in common. ... 

As shown in the previous chapter, the Tableau provided six classes for the genera of pure chemical substances one for the genera of simple substances and five for the genera of different types of compounds. This most principal feature of its classifica-tory strucmre relied on two premises. It was first assumed that the chemical substances in question could be divided into either simple substances or compounds and second, that all chemical compounds were classified according to their chemical composition. Classification according to composition is, therefore, the most fundamental chemical principle embodied in the classificatory structure of the table. 

The premise that all of the substances comprised by the Tableau s classificatory structure are either simple substances or compounds is not only an elementary presupposition for classification according to composition, it is at the same time the basic criterion for the selection of chemical substances that can be classified within this framework. The substances assembled in the tableau of the Methode represent a highly selected group of substances compared to the archipelago of materials—... 

For a historical understanding of this selection, its tacit character is particularly telling. In the text of the Methode it was not mentioned, let alone clarified, that the classificatory structure of the table implies a selection of chemical substances. Its authors argued neither for such a selection nor for the underlying distinction of the selected chemical substances from others. They evidently felt no need to justify this selection and, as a matter of fact, none of their contemporaries asked them to do so. From these circumstances one can conclude that both the tacit selection and its tacit criterion were not introduced by them for the first time. Rather, they proposed a new nomenclature and classification for a selection of substances that had been singled out and well established as a particular subject matter of chemical investigation independent of and long before their classificatory attempt. 

Coming across such an additional classificatory structure, it seems natural to ask, is only the class of acidifiable bases indicative of this stratum, or were other taxonomic units of the table also formed with respect to selected chemical syntheses And if so, with respect to which ones Which chemical syntheses stractured the classification of the table Or, more precisely, the interpretation of which specific syntheses provided an additional chemical framework of the Methode s classification, which governs its more concrete features ... 

The confrontation of the Tableau s classificatory structure with its phlogistic mirror brings to light another feature of the Methode s classification that might otherwise escape one s attention for the comparison of the two classifications shows that the classificatory structure derived from the conception of neutral salts need not necessarily fit with a classification according to composition. In the phlogistic scheme (the... 

The fact that the nomenclature presupposed the classification and not the other way around is also of immediate importance for the question of what role Lavoisier s Chemical Revolution played in the nomenclatural reform of the Methode. This transformation shaped the proposed nomenclature to precisely the extent to which it modified and complemented the traditional classificatory structure. The Chemical Revolution was not the foundation of the Methode s classification, even though it shaped certain essential features of it. Nor was the new chemical system the decisive prerequisite condition for the new nomenclature, although it unmistakably left its... 

The Periodic Table of elements is the most visible, and arguably the most fundamental, classificatory structure in chemistry. In its contemporary incarnation, the table serves to connect the realm of substances with the realm of atoms and... 

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