Contact electrification of solid particles

Solid particles carry with them electrostatic charges from contact with the storage vessel. The sign of the charge acquired in the air of the laboratory was determined for metal particles which were poured either from a silica bowl or from a glass beaker, and for particles of insulators and semiconductors which parted contact with containers of silica, glass or various metals. A closed, insulated, metal funnel which is connected to an electroscope receives the charge which the particles carry with them from contact with a container from which they are poured. When the particles are made to stream from the funnel after the electrostatic charge has been removed from it, the funnel again acquires a certain charge, while the particles carry the opposite charge with them to the receptacle. Copper filings poured from a container of either glass or silica assume a positive charge, and silica particles poured from a copper trough assume a negative charge, while silica in bulk assumes a positive charge when it is rubbed against copper in bulk. Antimony powder poured from a container of either glass or silica assumes a negative charge, and both glass and silica in bulk rubbed against a block of antimony assume a positive charge.