pressure between shaft 20 and the cylinder wall surrounding opening 22 input means such as conduit 24 are provided so that a carrier fluid such as nitrogen or steam may enter the lower portion of cylinder 11 in the direction of arrow 25 an exit tube 26 is provided in fluid communication within the space bounded by piston 16 and cylinder 11 so as to deliver fluidized solid particulates to a point where they will be mixed with a hydrocarbon feedstock piston 16 is provided with a cup like extension 30 so as to further define the space within cylinder 11 in which the fluidized solid particulates may occupy a suitable baffle 28 may be provided to prevent particles from splashing out of the cup in the event of vigorous fluidization when used in combination with baffle 28 extension 30 is dimensioned so as to telescope with baffle 28 although exaggerated in fig1 it is to be understood that the clearance x between piston 16 and cylinder 11 as well as the clearance y between the cup like extension 30 of piston 16 and baffles 28 are much smaller than actually shown a manual or remotely controllable valve 32 permits return of partially spent catalyst from stripper 34 to the source of solid particulate 12 the fluidized particulates exiting the particulate delivery system 14 via exit tube 26 travel in the direction of arrow 35 until they are mixed with the hydrocarbon feedstock introduced into reaction tube 36 from conduit 44 fig2 invention shows a cross sectional view of a solids dispensing device which is especially suited to single uses dispenser 100 consists of.