A powder feeder, especially useful for transporting particulate materials at very low, yet precisely controlled, rates. A container preferably a closed vessel, is provided with an orifice to admit gas up through the bottom of the vessel in a high velocity column (or jet). A pair of concentric conduits...http://www.google.ca/patents/US3987937?utm_source=gb-gplus-sharePatent US3987937 - Powder feeder and methods for transporting particulate material
