pratt] B1UQUETTING TESTS. 137 
gas plants, and (6) from petroleum gas tar. Pitches made from the 
first three varieties of tar were tested, and each gave practically as 
good satisfaction as the other when approximately of the same com- 
position. Petroleum gas tar gave the best results. 
There was considerable variation noticed in the pitches that were 
submitted to the plant for the experimental work, and at the begin- 
ning it was difficult to obtain the grade that was desired. The first 
pitch received was from the St. Louis works of the Barrett Manufac- 
turing Company. The pitch was too hard and would not soften at a 
sufficiently low temperature to be used satisfactorily in either the 
English or the American machine, it was subsequently proved that 
the pitch did not contain a sufficient quantity of the creosote oils to 
give it the required binding qualities. This pitch is designated pitch A 
throughout this report. The second lot of pitch was received from 
the Chatfield Manufacturing Company, of Carthage, Ohio. It was 
harder than pitch A, indicating that a still greater per cent of the 
creosote or adhesive oils had been driven off. Although these pitches 
would make briquettes, it was necessary to use from 13 to 18 per cent 
of them, while of a good, satisfactory pitch it required onty from 6 to 
9 per cent with the same coal. This pitch is designated throughout 
the report pitch X. 
In order to determine the quality of pitch that would be satisfactory, 
some of the best tar from the producer-gas plant was heated until all 
of the water was expelled. The boiling was continued until, when the 
residue was dropped into water having a temperature of 55° F., it 
became brittle. After bucking down, this pitch stuck together on 
standing one week in the laboratory. It is known throughout tins 
eport as pitch Z. A long series of tests was then made with this 
itch upon various coals, and it was found that 6 per cent of it made 
tter briquettes than 13 per cent of pitch X. In order to further 
emonstrate the necessity for pitches of the right quality to contain a 
ligher percentage of the creosote or adhesive oils than pitches A or X, 
experiments were made with hard pitch A and water-free producer-gas 
ax. These were melted together in various proportions until a prod- 
ict was obtained which, when dropped into water at 55° F., would 
)ecome brittle. A sufficient quantity of this product was made to 
priquette 2 tons of coal, and it was found to give the results desired, 
Ihowing that it is necessary for a pitch to contain a certain percentage 
»f these creosotes or adhesive oils. This pitch will soften when held 
n the mouth; when it is first bitten it cracks and crumbles like spruce 
[urn, but almost immediately becomes plastic and can be chewed 
ike ordinary gum. This pitch is designated throughout this report 
ntch Y. 
Samples of this pitch were sent to the Barrett Manufacturing Com- 
any and the Chatfield Manufacturing Company, and pitch of the right 
