I worked with Prof. John Baez on reaction networks at the Center for Quantum Technologies last summer. Here is an article which summarises what I was up to for the most part. It is concerned with how the master equation reduces to the rate equation in the limit where there are very large numbers of things of each kind. I also wrote an article on Coherence for Solutions of the Master Equation (https://johncarlosbaez.wordpress.com/2013/07/10/coherence-for-solutions-of-the-master-equation/) before. To know more about network theory, read John Baez’s book at http://math.ucr.edu/home/baez/stoch_stable.pdf. ]]>