GEAIN-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 tlie inflammability of dusts in this region, where the relative 

 humidity is usually above 50 per cent. 



Table 17. — Moisture contents of materials. 



Design.v 



Material. 



Series. 



tion. 



51 



11 



12' 



14 



15 



A 



Fine oat liulls 



Per cent. 

 9.6 

 9.8 

 8.9 



Per cent. 

 9.9 



Per cent. 

 5.7 



Per cent. 



Per cent. 



B 









C 



Oat hulls 





3.2 



9.2 



3.3 



D, 





14.1 

 9.3 

 9.0 





D. 



Flour (oven dried) . . 





10.2 

 5.7 





8.5 



F 





10. 4 

 9.9 

 8.6. 

 9.0 







G 









I 







1 



K 



Conveyor mixture.. 





1 



N 







5.2 







P 



Barley malt sprouts; 







9.4 

 12.0 

 9.4 



4.0 



Q-- 









3.5 



R 



Brewers' dried grain ... 







4.7 













lAlso 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 mr.ximum 

 moisture content above which the dusts can not be ignited. 



