ABSTRACT
Evaporation of liquids to a vapor state is well understood; vapor pressure relations determine what will occur, and molecular theory provides an explanation of the actual mechanism of evaporation. This chapter provides the word "pulvation" which is defined as the non-molecular mechanical or physical process whereby dust or mist becomes suspended in air from a previous state of rest. The pulvation action may merely disperse previously pulverized material from a state of rest to an air-borne state, or it may involve simultaneous reduction from a solid mass, like rock, to powder. It must be distinguished from the dispersion action of secondary air current, which may be violent or gentle like the random convection currents characteristic of all spaces. Rising hot air streams sometimes may occur in such a manner as to disperse the primary pulvation cloud, although such streams are usually integral with a contaminating action which is considered separately under the following subject of air induction.
