12 



The wide variations in quantity obtained from the same class of ma- 

 terials are due to differences in quality and weight of the wood used 

 and also to different methods of conducting the distillation. The low 

 yield obtained from sawdust is rather surprising, and is probably 

 explained by the packing of the material in the retorts, owing to 

 which fact complete decomposition is rarely obtained. As far as can 

 be learned no satisfactory process has yet been devised for distilling 

 sawdust. 



APPARATUS FOB DESTRUCTIVE DISTILLATION. 

 DESCRIPTION OF EQUIPMENT. 



The apparatus required for the destructive distillation of wood con- 

 sists of (1) retorts or ovens, in which the distillation is carried on and 



FIG. 1. Early form of kiln in which only charcoal is recovered. 



the chief chemical reactions involved in the production of the crude 

 products take place; (2) condensers, in which the condensable vapors 

 are liquefied; (3) stills, in which the crude products are separated, 



FIG. 2. Early form of kiln in which charcoal and tar are recovered. 



concentrated, and purified ; (4) mixing pans for the preparation of ace- 

 tate of lime, and (5) general apparatus, such as evaporating pans, 

 storage tanks, coolers, pumps, etc. 



[Cir. 36] 



