15() PRELIMINARY REPORT ON COAL-TESTING PLANT, [bull.261. 
sulphate. Eggettes of this same mixture made on the American j 
machine were practically the same in character and unusually dull 
grayish in appearance. The specific gravity of these briquettes was 
1.205. When tested upon the compression machine these briquettes, 1 
which were very crumbly and weak and broke rather readily in the 
fingers, compressed much more than usual before breaking. Their 
crushing strength was 5,600 pounds per square inch. Another ton 
was tried with per cent of pitch D, but the resulting briquettes were I 
practically the same as with 7 per cent, although a little darker in 
color. They also showed similar streaks of fire clay on the surface 
and their fracture was decidedly earthy. They weighed on the average 
7.5 pounds each. There seems to be but little adhesiveness between j 
this pitch and the dirty coal, and to make a good briquette with this j 
pitch it would be necessary to use probably as much as 15 per cent orl 
more. 
Satisfactory results with soft pitch not having been obtained, one! 
*on of this slack coal was tried with 8 per cent of the harder pitch A. j 
The bv*iouettes were well pressed and blacker than those with 7 perl 
cent of pitch D, but were not so strong. There was not the slightest 
tendency for the mixture to become stiff in the machine, which is a 
further indication of the destructive character of this coal on the 
properties of the pitch. 
This coal was next tried by mixing together 93 per cent of coal, 6jl 
per cent of rosin, and 1 per cent of quicklime. The lime was mixel 
in lumps from dust to three-fourths of an inch in diameter, which it 
was expected would be reduced by the disintegrator and slacked by 
the steam of the pug mill, so that the cement would not set too quickly. 
The disintegrator, however, had very little effect on the hard lime, 
and consequently there were many large unslaked pieces in the 
resulting briquettes, which caused them to fall to pieces. Some of i 
this material that remained in the pug mill for some time gave a bri- 
quette that was hard while hot, but after cooling the briquette became 
earthy. These briquettes weighed on an average 7 pounds each. The 
eggettes made of this material were dense, but very crumbly. 
In order to overcome the chances of unslaked lime going into thei 
briquettes, the lime was slaked before using with one-half its weight j 
of water, making a fine, dry powder. This was mixed with the coa 
to give the same proportions with the rosin as in the above test, anc 
although the briquettes were smooth and well formed, having beer 
thoroughly pressed, they were crumbly and not at all strong. Tha 
were grayish in color and similar in quality to those made with 7 pel 
cent pitch D. They weighed on an average 7.5 pounds each. Th 
eggettes of this same material were very crumbly and dull in luster. 
Some of these lime-rosin briquettes were burned, and they wer 
