GRAIN-DUST EXPLOSIONS. 
Conclusions: There is no positive indication in the present series 
of tests that the humidity of the atmosphere has any material effect 
on the inflammability of dusts in this region, where the relative 
humidity is usually above 50 per cent. 
Table 17. — Moisture contents of materials. 
Designa- 
MateriaL 
Series. 
tion. 
5i 
11 
12 
14 
15 
A 
Per cent. 
9.6 
9.8 
8.9 
Per cent. 
9.9 
Per cent. 
5.7 
Per cent. 
Per cent. 
B 
c 
3.2 
9.2 
3.3 
D[ 
14.1 
9.3 
9.0 
D 
10.2 
5.7 
8.5 
F 
10.4 
9.9 
8.6 
9.0 
G 
Corn 
I 
I 
K 
N ' 
5.2 
P... 
9.4 
12.0 
9.4 
4.0 
Q 
R. 
3.5 
4.7 
1 
x Also typical of the first 9 series. 
EFFECT OF MOISTURE CONTENT OF MATERIALS. 
Table 17 gives the results of moisture determinations made in 
several tests. Average samples were obtained during the feeding of 
the materials into the attrition mill, and were kept in carefully 
stoppered bottles. The method for making the moisture determina- 
tions was similar to that employed for coal analysis, in which the 
samples are placed in a constant temperature oven at 220° F. The 
crucibles containing the samples were weighed, by means of analytical 
balances, at frequent intervals of time until the material was dried 
out, as indicated by two successive weights of practically the same 
value. The percentage of moisture was then calculated on the basis 
of the original wet sample. Duplicate determinations were made in 
each case. 
The number of moisture determinations and the range of moisture 
contents were not sufficient to enable one to draw any positive con- 
clusions, but, in the case of oven-dried flour at least, a tendency 
toward more regularity and violence of explosions was noted. Un- 
doubtedly the same tendency would be noted in all grains if the con- 
ditions of testing could be properly controlled, and it would perhaps 
be advisable to determine the minimum amount of moisture to ren- 
der the material noninflammable. For the present it seems that the 
following conclusions may safely be drawn : 
1. The less moisture a dust contains, the more inflammable it is 
likely to be. 
2. It is probable that for inflammable dusts there is a maximum 
moisture content above which the dusts can not be ignited. 
