A Tagmemic Semiotic Analysis of Chemical Representations

Abstract

A semiotic analysis of chemical formulas and reactions using tagmemic theory discloses many features relevant for semiotic structure. Among these are the etic/emic distinction; the presence of units, hierarchy, and specific system contexts; the relevance of particle, wave, and field perspectives; contrast, variation, and distribution in units; filler, prominence, and function in the hierarchy.  In chemical representations, a principal hierarchy of three levels is spelled out: (i) the level of the smallest units, which includes the signs for the chemical elements, (ii) the level of the formulas for molecular compounds, and (iii) the level of equations for chemical reactions. Further, it is argued that chemists use not one but four distinct kinds of semiotic systems in describing these three levels: (a) formulas like H₂O to describe molecules; (b) descriptions using special technical vocabulary; (c) stick diagrams in two dimensions; and (d) three-dimensional models with balls representing the atoms. There are also hybrid descriptions that use resources from more than one of the four distinct systems. The analogous structural features that belong to chemical formulas, on the one hand, and natural languages, on the other hand, show that such a semiotic analysis of chemical formulas is appropriate and fruitful.