16 
EXPERIMENTAL WORK IN FUEL TESTING. 
Changes in moisture content of sample (No. 1639 C) of well-dried Illinois coal — Continued. 
SECOND SERIES— 10 GRAMS ON 4-INCH WATCH GLASS. 
Air of laboratory. 
Time interval between weighings. 
weight. 
Tempera- 
ture. 
Humid- 
ity. 
Grams. 
-0. 0190 
- .0120 
- .0175 
- .0280 
+ .1235 
+ .0195 
- .0580 
- .0280 
Per cent. 
-0.19 
- .12 
- .175 
- .28 
+1.24 
+ .20 
- .58 
- .28 
° C. 
28 
Per cent. 
36 
25 
18 
27 
32 
63 
2 davs 
64 
35 
41 
0.18 
THIRD SERIES— 8.3 GRAMS IN OPEN, WIDE-MOUTHED 2-OUNCE BOTTLE. 
+0.0015 
+ .0010 
- .0000 
+ .0080 
+ .0230 
- .0000 
+ .0240 
- .0175 
- .0000 
+ 0.02 
+ .01 
23 
69 
+ .08 
+ .29 
25 
18 
63 
64 
+ .29 
- .21 
- .00 
27 
32 
35 
41 
Total gain in 20 days 
0.48 
An inspection of these results shows that in samples of fine coal 
prepared from coal not previously air dried the loss may be rapid, 
being in a 1-gram portion of undried sample over 2 per cent in five 
minutes and over 8 per cent in twenty-four hours. That samples kept 
in bottles may lose a considerable amount of moisture unless tightly 
stoppered is also shown by the results obtained from weighing the 
samples in an open bottle, the loss in twent\^-four hours being nearty 
0.7 per cent and in seventy-two hours almost 2 per cent. This loss 
continued until the total loss in twenty-four days was about 5 per 
cent. That the danger from losses in handling a fine sample which 
has been well air dried is not nearly so great is shown by the tests 
upon No. 1639 C. Upon the 1-gram portion of this sample the loss in 
five minutes was 0.93 per cent, but the additional loss afterwards was 
small, showing that the sample was not far from air dry under the 
existing conditions. In fact, under the conditions existing on the 
next afternoon the sample as ground was drier than air dry, as is 
shown by an increase of over 1 per cent in weight. That this sample 
was about air dry, under the average conditions existing, is further- 
more shown by the results obtained on the sample exposed in an open 
bottle, where the sample at different times shows small losses and 
small gains in weight. The rapidity with which the 1-gram portion 
of this dried sample gave up the little moisture it possessed over and 
above the existing air-dry conditions shows the extreme sensitiveness 
of finely ground coal samples to changes in the moisture. content of 
the air. 
