In a recent paper [Khumalo, N., Glasser, D., Hildebrandt, D., Hausberger, B., Kauchali, S., 2006. The application of the attainable region analysis to comminution. Chemical Engineering Science 61, 5969-5980] it was shown that the attainable region approach could prove useful in designing better comminution circuits. Fundamental to this approach was the assumption that the rate of comminution was only determined by the specific energy within the device. This paper shows experimentally that this assumption holds for a batch ball mill. The system presented here considered breakage of mono-sized feed particles in a laboratory ball mill into two distinct progeny size classes. The population balance model was successfully used to model the experimental products and the results were represented geometrically in a two-dimensional space. The resulting geometric structure can be used to solve process synthesis and optimization problems simultaneously. It was found that the breakage rate parameter out of size class I changes with time but exhibits an exponential relationship with an asymptote. It is hypothesized that this asymptote is the rate of breakage at long grind times or in well-mixed, steady-state continuous systems. It is shown that the parameters of the process depend only on the specific energy. This was one of the assumptions that was made in the construction of the attainable region. Thus, equipment selection and operating conditions only require one to match the required specific energy. (c) 2007 Elsevier Ltd. All rights reserved.