¥76 



Popular Science Monthly 



more volatile gases first and the heavy ones 

 afterward. This treatment of coal tar is 

 combined with alternate treatment by 

 certain chemicals, commonly referred to 

 as reagents. These reagents consist of 

 dilute caustic soda, dilute acid and con- 

 centrated sulphuric acid. 



When distilled up to 252 deg. Fahr., ben- 

 zene, more frequently referred to as benzol, 

 is obtained. 

 It is the first 

 to pass over. 

 By further 

 distillation , 

 up to 306 deg. 

 Fahr., sol- 

 vent and 

 burn ing- 

 naphtha are 

 also driven 

 out. Still 

 further heat- 

 ing from 414 

 deg. to 486 

 deg. Fahr., 

 results in the 

 formation of 

 creosote and other oils, referred to as the 

 heavy oils. 



Beyond these are obtained anthracene 

 oil and anthracene, both used in making 

 dyes. Other products are lampblack, used 

 in making printer's ink; pitch, employed 

 for roofing, road-building, water-proofing; 

 and coke, used instead of coal for obtaining 

 intense heat without smoke, especially in 

 blast furnaces. In 1916, 54,200,000 tons of 

 coke were manufactured in the United 

 States. 



A beehive coke oven. The coal is admitted at the top and the 

 coke removed through the side openings. By this crude method, 

 the tar and ammonia are entirely wasted, passing off into the air 



Benzol Obtained from Gas or Tar 



In the case of coke oven gas, benzene (or 

 benzol) is obtained by a direct recovery 

 method. The recovery of benzol is limited 

 almost entirely to the coke oven plant and 

 to the tar distiller. The chart on page 874 

 shows how benzol can be obtained directly 

 from raw gas or indirectly from the raw tar. 

 During the distillation of tar the so- 

 called light, 

 middle and 

 heavy oils 

 which come 

 off give us 

 the first nine 

 dye"crudes," 

 such as ben- 

 zol, toluol, 

 xylol, naph- 

 thalene. By 

 addition and 

 subtraction 

 of various 

 chem icals, 

 and by cer- 

 tain chemical 

 changes-, 

 these crudes make up the 300 dye "inter- 

 mediates," such as phenol, aniline, cresol, 

 etc. These, by further addition and sub- 

 traction, make the 1200 different coal tar 

 derivative dyes. 



These colors range from black up through 

 the rainbow colors and other shades, such 

 as the browns and grays. In fact, to tell 

 the difference between two similar shades 

 is like splitting hairs. In the chart, page 

 879, I have shown only the production 

 of basic reds. 



A battery of by-product ovens. Observe two trams, the upper one for depositing coal in the 

 ovens and the lower one for ramming the -coke out on the farther side. The ovens are sealed 

 with a clay-packed lid. Half the gas formed is consumed in heating the coal. The remainder, 

 as well as the tar and ammonia, is conducted away through pipe lines to the receiving tanks 



