The box was filled nearly, but not quite full, of granulated hard carbon.
This salt is also formed by dissolving tin in strong hydrochloric acid and allowing it to crystallize, and is industrially prepared by passing sufficiently hydrated hydrochloric acid gas over granulated tin contained in stoneware bottles and evaporating the concentrated solution produced in tin basins over granulated tin.
Granulated cork has practically the same insulating properties as silicate cotton, and the same thicknesses may be used.
In Norwood and Rogers's process a thin coating of tin is applied to the iron before it is dipped in the zinc, by putting the plates between layers of granulated tin in a wooden tank containing a dilute solution of stannous chloride, when tin is deposited on them by galvanic action.
The current from the battery used passed from the diaphragm through the granulated carbon to the metallic back of the box.