44 



management, fuel); cost of containers for shipping products; insur- 

 ance, depreciation, and repairs; interest on capital, etc. 



It is beside the purpose of this circular to give an estimate of these 

 gross values and fixed charges, and they are only mentioned here in 

 order to point out briefly and in general terms some of the ways in 

 which an inspection of numerous plants and laboratory work indi- 

 cates that the net proceeds of several of the industries may be 

 increased. Attention will be confined to a consideration of (1) 

 yields, (2) operating expenses, (3) raw materials. As a matter of 

 fact, however, these three headings are so intimately associated that 

 the effect of any one of them on profits can not be entirely differenti- 

 ated from that of the others. 



YIELDS. 



In the destructive distillation of wood the yields obtained in prac- 

 tice are much below those given under laboratory conditions. This 

 may be due to destruction caused by local overheating in the retorts, 

 loss of vapors around the doors of the retorts, incomplete carboniza- 

 tion, or imperfect condensation. Losses may also occur from incom- 

 plete or excessive overneutralization of acids with milk of lime, or to 

 incomplete separation of alcohol and acids from the tar, or of alcohol 

 from water. All of these points should receive the constant watchful 

 attention of the superintendent, that such losses may be reduced to a 

 minimum. Indeed, yields are largely controlled by the experience 

 and technical knowledge of the superintendent. The almost total 

 absence of chemical control in these industries doubtless accounts for 

 many unprofitable plants, the source of whose failure can not be 

 otherwise discovered. 



OPERATING EXPENSES. 



Inspection of destructive distillation plants leads to the conclusion 

 that the expense of operating is largely increased by the employment 

 of hand labor where machinery could often be used to better advan- 

 tage. Thus, wood received is often handled several times before it is 

 placed in the retorts. Nearly all round retorts are filled and emptied 

 by hand. Storage room should be so arranged as to avoid handling 

 the wood more than once after it is received. This is possible only 

 when oven retorts are used, in which case the wood is not handled 

 except when loaded on the retort cars, which are moved by power 

 and emptied directly into railroad cars or storage bins, from which the 

 charcoal may be taken automatically. 



Great loss of heat and waste of fuel is occasioned by the practice of 

 condensing and cooling to ordinary temperature the aqueous distillate 

 (p. 32) and allowing it to stand for the -purpose of settling out the tar. 



[Cir. 36] 



