94 



CHEMICAL MANUEES. 



triturating plates and the quality of the metal used render them 

 almost everlasting. The elevations (? incline) from one stage to 

 another are fitted with orifices which allow the sufficiently ground 

 material to escape. These orifices can be regulated from the out- 



FiG. 10. — Section of Pfeiffer's Crusher- Separator. 



«ide. They may be contracted or enlarged as required, so as to 

 reduce the material to the required degree of fineness. As in 

 ordinary ball mills, the wrought-iron cover which surrounds the 

 drum ends in its lower part in a hopper ; this collects the ground 

 material and leads it to a cup elevator, which conveys it to an air 



