Spin crossover(SCO)compounds are of great interest for data storage materials due to their highly reversible switching between spin states1.Each spin state exhibits different magnetic properties the magnitude of which is dictated by the size of the SCO particle.Nanoparticles are of particular interest in this area2 but size control of these compounds can be difficult to exact.Using the Vapourtec R-Series Flow Reactor with a range of tubing(1 mm ID open tubing,3.2 and 6.8 mm ID tubing with static mixer inserts)we have optimised the production of [Fe(Htrz)2(trz)](BF4)nanoparticles.