When modelling asynchronous circuits as a chemical system, the wires are chemical species from the output set of one gate component to the input set of another. We cannot bound the time for a gate to transform an input species to an output species. This excludes the class of self-timed circuits. Under deterministic semantics, we could guarantee an isochronous fork since two chemical species, either high or low, could theoretically reach the threshold M at precisely the same time given equal rates and initial concentrations, and therefore under deterministic semantics we have a Turing-complete method of computation. We cannot guarantee this under stochastic semantics (Cook et al. 2009). This is because there is a non-zero probability that one species could reach M before the other. We thus conclude that our circuits, at worst, can be classified as speed independent. We can calculate approximately the delay on wires based upon rates and concentrations for each semantics.