tATT.j BRIQUETTING TESTS. L49 
led and probably contained nearer 15 per cent than 1 1 per cent pitch." 
hi account of the difficulty of setting- the machine to feed accurate 
ercentages of pitch to the coal, the experiments were conducted for 
ae most part after this by weighing out the determined quantities 
f coal and pitch by hand. Pitch X, on account of its hardness, set 
jo quickly in the molds, so that the briquettes were insufficiently 
ressed and apt to be porous. 
Arkansas No. 3. — This coal was briquetted without running it 
irough the drier with 9.5 per cent of the hard pitch X, which was 
3iind to be plenty for this coal. The coal was slightly moist, which 
lade it in just the right condition to pass readily through the machine 
r ithout clogging the elevator. The coal was very friable and was 
sduced to almost a flour in the disintegrator. The briquettes had 
ery smooth, polished surfaces, having received the greatest pressure 
lat could be obtained from the machine. Some of the briquettes, as 
ley were received from the machine, were cracked perpendicularly 
> the pressure, which may have been due to an excess of pressure. 
hese briquettes weighed on an average 6.8 pounds each. 
This coal was also tested with the somewhat softer pitch A. One 
>n of the coal was mixed with 8.7 per cent of pitch. A large excess 
steam was introduced into the pug mill so as to soften the pitch as 
uch as possible. The briquettes were smooth and easily handled, 
it somewhat pitchy, showing that there was an excess of pitch. 
nder the same conditions of heat and pressure, 7.5 per cent of pitch 
would have been sufficient, and if a good pitch were used a still 
nailer amount would make a good commercial briquette. These 
iquettes ignited readily and did not disintegrate in the fire until 
ey were consumed." 
Arkansas JYo. 4- — This consisted of slack coal, which was soaking 
et when received, and it had to be passed through the drier before it 
uld be used. When dried, it was so brittle that the disintegrators 
the English machine reduced it to flour, so that it choked up the 
evator and other parts of the machine. The first run made of this 
ied coal contained 12 per cent of hard pitch X, and although the 
iquettes when first received from the machine were very compact 
d smooth, they were incoherent and unsatisfactory and on exposure 
the weather very soon began to disintegrate more or less and became 
liable. The next test on this very finely divided coal was with pitch 
One ton was mixed with 10 per cent of pitch. The press was run 
ster, not only to make the pressure greater, but also to give the 
rd pitch less time to set in the machine. At the same time the dis- 
tegrator was run slower in order not to reduce the coal to so 
e a condition. The briquettes were very pitchy, but owing to the 
'tcess of water from the condensation, many cracked when the 
" For strain test see p. 80. 
