24 



BULLETIN" 1036, V. S. DEPAETMENT OF AGRICULTUEE. 



tar from YougMogheny and five from Westmoreland. In addition, 

 three samples were taken from plants using Alabama coal and three 

 from plants using mixed coal in the horizontal retorts. Certain 

 earlier investigations at the Forest Products Laboratory had shown 

 that the tar produced from at least one inclined-retort plant had 

 certain peculiarities which at the time put it under the suspicion of 

 having been contaminated with other tars. For this reason it 

 seemed desirable to visit as many of these plants as could be con- 

 veniently reached and determine whether these differences in proper- 

 ties were peculiar to the one plant or whether they were character- 

 istic of inclined-retort tar. Six samples of this tar were collected. 

 At the time of the collection only two plants were using the vertical 

 retort, and one of these was not in active operation. Therefore, only 

 one sample of vertical -retort tar was taken. Approximately one- 

 half of the by-product coke-oven plants then existing were visited. 

 They included six Semet-Solvay, five Otto or Otto-Hoffman, and one 

 Koppers oven plant. 



Table 8 shows the maximum temperature at which the coal was 

 coked, and the specific gravity and free-carbon content of the tar 

 produced by the different types of oven, as determined by the Office 

 of Public Roads in 1912. 



Table 8. — Specific gravity and free-carbon content of various coke-oven tars. 



Type of oven. 



Maximum 



temperature 



of coal 



r C). 



Specific 

 gravity 

 of tar at 

 25° C. 



Free- 

 carbon 

 con- 

 tent. 



Tyi^e of oven. 



Maximum 



temperature 



of coal 



(°C.). 



Specific 



gravity 



of tar at 



25° C. 



Free- 

 carbon 

 con- 

 tent. 





1, 388 

 880 to 950 

 950 to 1, 150 

 950 to 1, 150 

 950 to 1, 150 

 950 to 1, 150 

 950 to 1, 1.50 

 950 to 1, 150 

 950 to 1, 150 

 950 to 1,1.50 

 950 to 1, 150 

 950 to 1, 150 

 950 to 1, 150 

 950 to 1, 150 



1.171 

 1.169 

 1.195 

 1.206 

 1.176 

 1.168 

 1.173 

 1.191 

 1.169 

 1.159 

 1.181 

 1.159 

 1.141 

 1.175 



3.89 

 2.73 

 7.76 

 8.77 

 7.14 

 6.10 

 4.71 

 7.49 

 6.56 

 6.07 

 8.85 

 5.05 

 3.96 

 6.90 



otto-Hoffmann 



Do 



Do 



1, 200 

 1,000 



1.160 

 1.214 

 1.143 

 1.160 

 1.191 

 1.179 

 1. 133 

 1.176 

 1.195 



1.182 

 1.211 



1.210 



13.94 



Do 



14.05 



Semet-Solvay 



Do 



10.81 



Do 



United Otto 



Do 



1,111 

 1,444 

 1,222 

 1,222 

 1,222 



8.37 



Do 



7.89 



Do 



8.49 



Do . ... 



Do 



5.21 



Do 



Do 



10.53 



Do 



Do 



12.18 



Do . . 



United Otto and 



Otto-HofTmann . . 



Do 



833 to 1, 055 

 1,111 



1,000 





Do 



11.30 



Do 



12.40 



Do 



United Otto and 

 Rothberg 





Do 



16.80 







Attention is particularly directed to the low carbon content of 

 these tars. Of the 26 listed, only 8 have more than 10 per cent. 



A total of 36 specimens of coal tar reached the Forest Products 

 Laboratory in good condition. Three specimens were lost thi'ough 

 leakage m transit. Table 9 gives the type of retort or oven from 

 which the specimen tars were obtained, the land of coal used, and a 

 rough measure of the temperature used in coking. The tempera- 

 tures shown for by-product tar were those given in Circular 97 of 

 the Office of Public Roads for the same plants. For the most part 



