AbstractElectrostatic processing of raw potash salt. The paper traces historical development of the electrostatic separation process. The process development by the German potash industry is definitely based on contact charging. Intensity and sign of charge imparted to the individual salt minerals can be precisely influenced by treatment of the salt with chemicals and, at the same time, also with air of a defined relative humidity. The development of efficient free‐fall separators was of importance for the technical realization of the process. These separators contain electrodes about 2 m long which consist either of circulating, specially coated rubber bands or of a row of tubes positioned vertically next to each other which rotate continuously around their own axes. Charging of the salt minerals is very probably effected by electron transition. The paper describes tests carried out in high vacuum on KCl (100) and NaCl(100) surfaces for interpretation of the charging operatio