40 



BULLETIIT 1036, TJ. S. DEPAETMEISTT OF AGRICULTURE. 



tar creosotes indicated by figures 18 to 20 must, therefore, be due 

 either to the type of retort or to the temperature of coking. 



Figure 22 shows two coal-tar creosotes produced from tars from 

 the same mixture of £oal and operated under the same management, 

 and as nearly as possible at the same temperature, although one tar 

 was produced in an incliued retort and the other in o. horizontal 





























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2£0 280 

 TEmPERATURE — 'C 



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Fig. 20. — SuJphouatioii residues of fractions of authentic coa'.-tar creosotes. 



A. Horizontal-retort tar creosote.;. 



B. Inclined-retort tar creosotes. 

 Dotted line — Vertical-retort tarcreoso'.e. 



C. Semet-Solvay tar creosotes. 



D. Ottotarcreosotes. 



Dotted line — Koppers tar creosotes. 



retort. Figure 23 shows two coal-tar creosotes obtained from the 

 same mixture of coal at different by-product plants wliich were at 

 the time producing coke in approximately the same length of time, 

 but which' employ different types of oven — the Otto-PIoffman and 

 the Semet-Solvay. These figures show the effect of different types 

 of retort when the other two variables are practically the same. It 

 is noted that the results are nearly identical, or, at least, that there 



