PART n. EXPERIMENTAL COMPARISON OF AUTHENTIC 
SPECIMENS OF CREOSOTE. 
CHAPTER I. COLLECTING AND TESTING THE SPECIMENS OF CREOSOTE. 
In the early part of 1911 experiments were begun at the Forest 
Products Laboratory for the purpose of obtaining data on the 
chemical and physical properties of authentic coal-tar and water- 
gas-tar creosotes in order to check up the results previously obtained 
by the laboratory, and also of determining how wide a variation in 
these properties may be expected from the different retorts or ovens 
under various conditions of heating and with the different kinds of 
coal used. At the time the experiments were begun the latest 
available figures for the production of tar were the following: 
Gallons. 
Gas-house tar, 1908 58, 541, 000 
Coke-oven tar, 1909 60, 126, 000 
Water-gas tar, 1908 14, 700, 000 
The production of gas-house tar and that of coke-oven tar were, 
therefore, about equal, and the water-gas tar produced was about 
one-fourth of the product of the gas-house industry. 
MATERIAL USED. 
In collecting the samples of coal tar for this work the following 
points were taken into consideration: First, the type of retort or by- 
product oven employed; second, the kind of coal used; third, the 
temperature of coking. Circular letters were sent out to all the gas 
plants in this country that were manufacturing over 20,000,000 cubic 
feet of coal gas a year, asking for information on these points. Over 
75 per cent of the companies replied. Of a total of 91 gas houses 
using coal, 82 used the horizontal retort, 7 the inclined retort, and 
2 the vertical retort. Westmoreland coal was used by 19 of these, 
Youghiogheny by 35, Alabama by 7, Tennessee by 2, and the re- 
mainder were using mixtures of coal from different localities, chiefly 
mixtures of Westmoreland, Youghiogheny, and West Virginia, with 
other coals. Very few replies were made concerning the tempera- 
ture, except in such terms as white, orange, cherry, and red heat. 
In the few instances given, the temperatures ranged from 1,800° F. 
(982° C.) to 2,700° F. (1,482° C). 
In view of the predominance of Youghiogheny and Westmoreland 
coal in the gas-house industry, it was decided to take six samples of 
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