Rittinger’s constant for a synthetic opiate material with a density of 1.32 g.cm–3 is 28 Jm–2. A ball mill with a power consumption quoted at 37.5 kWh/tonne is used to comminute this material from an initial particle size of approximately 2.5 mm. If the particles are milled for ten minutes, assuming Rittinger’s hypothesis applies, what will their average diameter be at the end of the process?