32 ILLINOIS ACADEMY OF SCIENCE 



in fines in the coal means a distinct loss in value. The prob- 

 lem, therefore, was to test Illinois coals from the different dis- 

 tricts, under varying conditions, to discover any laws govern- 

 ing this breakage, and to establish some standard of relative 

 friability by which the reduction in market value due to degra- 

 dation might be impartially estimated. 



PROCEDURE 



The procedure involved a search of literature on the sub- 

 ject and a study of any methods and apparatus which had 

 been used previously. After testing some of these methods 

 they were rejected as unsuited to the problem, and new appa- 

 ratus devised. 



A drop test machine was constructed, in which a box filled 

 with 50-100 pounds of the coal to be tested and provided with 

 a gate on the bottom is elevated to any height up to ten feet 

 above the floor. 



The gate is opened suddenly and the coal falls to the floor, 

 which may be wooden, steel or concrete. By screening this 

 coal through a standard set of screens the breakage of the 

 larger sizes into the smaller is determined quantitatively. A 

 great deal of care is necessary in manipulation to secure results 

 which are in agreement. 



RESULTS 



The results have shown a surprising individuality among 

 different coals in regard to their comparative friability. It 

 seems possible to give definite coal of definite size a fixed com- 

 parative friability factor. The difference among Illinois bitu- 

 minous coals in themselves is about as great as between anthra- 

 cite and the least friable of the Illinois coals. A great differ- 

 ence was noted as to the material of the floor on which the 

 falling coal struck. Steel and concrete causing much more 

 breakage than wooden floors or bins. The size of the coal 

 and the amount of moisture present in the coal are other 

 important factors. For example, it was found possible to 

 place coal in water for a minute or two and greatly reduce the 

 amount of breakage. 



