pratt.] BRIQTJETTITO TESTS. 157 
found to give loss smoke than those with the rosin and no lime, and 
some less ev r en than those with pitch alone. 
Another test of this coal was made with rosin and Kansas crude oil. 
The experiments in the laboratory had shown that the best results 
could be obtained by using 6 per cent rosin and 1 per cent of the oil. 
In preparing this combination for the English machine, the oil was 
first mixed with five times its weight of line coal, so as to make a noii- 
sticky mass that would readily mix with the cracked rosin and coal in 
the usual manner. On account of the rosin becoming very fluid at 
212° F., the hot briquettes as they were received from the machine 
had no strength, and cracked slightly under their own weight when 
piled only two high. They also cracked rather badly owing to the 
water from the wet steam. On cooling they became strong and were 
of good quality. Some of the mixture that was allowed to stand in the 
mold before pressing until cool enough to be plastic was very good as 
received from the machine, but it had not been sufficiently pressed. 
On standing, these briquettes became coated with a heavy brownish- 
gray efflorescence. The weight of these briquettes averaged 7.29 
pounds each and their specific gravity was 1.25. The crushing strength 
of the briquettes was on the average 6,400 pounds per square inch. 
On account, however, of the lack of uniformity of the briquettes, the 
results of 8 tests varied from 1,300 to 9,210 pounds. The eggettes 
made from this same mixture were hard and compact, although of a 
lull color, and they had a good degree of strength as received from 
the machine. With an arrangement for cooling the mass after it has 
msscd through the pug mill and before being fed to the press, this 
uixture would make briquettes which would be very good physically, 
jut which would smoke rather badly. 
Since the above tests showed that the best way to counteract the 
iffect of the large amount of fire clay in this coal was to add some 
liquid binder which would soak into it and yet at the same time unite 
frith the solid binder, another test was made with creosote as a liquid 
binder and pitch as the hard binder. For this purpose Indian Territory 
^o. fi coal was mixed with 8 per cent pitch G and li percent of creosote, 
such as is used in preserving timber. The creosote and five times 
ts weight of fine coal were first mixed together and then thoroughly 
nixed with the cracked pitch and coal. In operating the machine 
vith this mixture, the amount of steam used for heating the mix- 
ure was gradually increased until there was an excess. This, how- 
ver, had no effect upon the cooled briquettes, but it made the hotter 
►nes more tender and a little harder to handle. The first briquettes 
>f this mixture cracked a little, due to excess of water, but the remain- 
er came from the machine strong enough to bear handling at once, 
he effect of the excess of steam was to insure more complete soften- 
g of the pitch and more uniform mixing of the clay. These bri- 
