15 



with an air space between. They are provided with large doors clos- 

 ing air tight and are heated by wood, charcoal, coal, or gas. 



The plant may be assembled and arranged in any desired manner, 

 but it is highly desirable that full advantage be taken of natural con- 

 ditions, that as much labor as possible be performed by machinery, 

 and that the whole establishment be conducted under the most rigid 

 control, in order that the plant may be profitably worked and losses at 

 any point quickly discovered. Modern plants are equipped with 

 either the round or oven retorts. Figures 10, 11, and 12 show 

 arrangements of such plants as found in American and German 

 practice. 



The condensers (fig. 7) are of the greatest importance; they should 

 be sufficiently large to condense all the products even under the most 

 adverse conditions, as material lost at this stage can never be recov- 

 ered. For separating the constituents of the distillate a simple still, 



D C 



FIG. 7. Types of condensers. 



such as is used in the preparation of distilled liquors, may be used, 

 although an iron still is generally preferred in distilling the alcohol 

 and acetone from the acetate of lime. For tar storage and settling 

 tanks it is customary to use wood; all pipes, pumps, and other 

 apparatus through which the acid liquors pass must be of copper or 

 wood. 



COST OF PLANT. 



Only approximate figures can be given as to cost and quantity of 

 equipment for the destructive distillation of wood, as any figures w^ould 

 be greatly modified by the location of the plant, local price of labor, 

 freight charges, royalties on patents, and completeness of equipment. 

 The first cost of equipment may often be greatly reduced by cheap 

 construction and by omitting many labor and time saving devices in 



[Cir. 36] 



