<p>A scientific law generally models the behaviour associated with some physical phenomenon such that it can be described in terms of y = m<i>x</i> + c. The turn of the ninetieth century saw the introduction of the laws of chemical composition and Dalton’s postulates, but these ideas are very different and cannot be assessed using the techniques of continuous mathematics. In this paper we review Dalton’s postulates and the corresponding types of chemical reaction process in the light of cellular automata and Wolfram’s new kind of science (NKS). We find that the bond forming, bond breaking and substitution (STAD) mechanistic steps that occur during chemical reactions have a broad correspondence with the rules of cellular automata, a concept of discrete mathematics. Wolfram identified that cellular automata have four general classes of behaviour, likewise, we propose that chemical reaction processes can be grouped into four corresponding rather general classes.</p>