The correct addition sequence can be crucial to the success of a process, including the sequence of adding solids and solvents.  Charging solids to a reactor containing a flammable solvent can build up an electric charge, and subsequent discharge can ignite vapors above the solvent; for this reason solvents are usually added to an inerted vessel after solids have been charged.  Sometimes when solvent is added second the solids clump and are poorly suspended, changing the availability of  the solids for subsequent reaction.  When conducting a use-test make sure to follow the addition sequence that will be used on scale-up.