42 



BrULETIX 1036, U. S. DEPAETMEXT OF AGRICrLTUEE. 



high, physical properties and having no sulphonation residues; but 

 that those subjected to lower temperatures yielded coal-tar creosotes 

 having lower index of refraction values and higher sulphonation 

 residues. The inclined-retort tar creosotes were higher in sulphona- 

 tion residues, and it seems to be almost universally true that, when 

 this type of retort is discharged, there is a small amount of uncoked 

 coal in the charge. In the vertical retort there is less chance for the 

















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220 240 260 280 



300 320 220 240 



TEMPERATURE °C 



280 300 



320 



Fig. 22.— Phj'sical and chemical constants of 

 creosotes obtained from tar produced from 

 the same mixture of coal at the same tem- 

 perature but in different types of retort. 



1. Horizontal-retort tar creosote. 



2. Inclined-retort tar creosote. 



Fig. 23.— Physical and chemical constants 

 of creosote's obtained from tar produced 

 from the samemistureof coalatthesame 

 temperature but in different typesof oven. 



1. Semet-Solvay tar creosote. 



2. Otto-Hoflmau tar creosote. 



gases to come in contact with the heated walls of the chamber imless 

 a fixing chamber is left above the charge. In the by-product ovens 

 the vertically heated ovens usually have a hotter roof than those 

 heated horizontally. Of the six vertically heated by-product ovens 

 only two produced coal-tar creosotes having a measurable amount of 

 sulphonation residue. Of five coal-tar creosotes from horizontally 

 heated ovens all but one had a measurable sulphonation residue. Of 

 the four that had sulphonation residue the oldest plant produced the 

 coal-tar creosotes having the highest stilphonation residue and the 



