THE FORGOTTEN TOOL - THE DESIGN AND USE OF MOLECULAR-MODELS

Since the inception of the modern atomic theory, chemists have used ph ysical models to represent the structure of molecules. The goal of thi s paper is to bring molecular modelling into focus as a constitutive y et overlooked element of chemical practices. It begins with a short te chnical introduction to molecular models, and then moves into a partic ipant-centred analysis of molecular modelling. Central points of this analysis include, first, a discussion of the dichotomy between graphic al and material forms of representation, with suggestions about its co nsequences for a semiotically-centred view of scientific activity; and , second, a look at the problem of the interpretation of molecular mod els, as discussed in the chemical literature. The last section focuses on the design of modelling systems through two related historical cas e studies - namely, the production of two space-filling modelling kits developed in the United States between the late 1930s and the late 19 60s.