46 WASHING, COKING, AND CUPOLA TESTS. 
amount of coke are worse than useless — in fact, misleading. Even 
if coke is selected the whole height of the charge and tests are made 
on cubes in number representing the number of inches the results 
still show only the strength of the one piece of coke from some par- 
ticular part of the oven and it is practically impossible to procure 
even approximately similar results from other pieces taken from 
different places. The condition of burning, the quenching either 
inside or out, and any number of factors which it is not possible to 
know, much less control, make different portions of the same oven 
vary greatly. 
A simple calculation will show that coke with a compressive 
strength of 48 pounds will support the burden of any modern furnace ; 
consequently this test gives no data of practical value. Moreover, 
there are so many other factors, such as action of heat and gases, attri- 
tion of coke against coke, against other ingredients of charge, and 
against the side walls, etc., that any calculation to show the burden- 
bearing capacity of the coke, even if it were possible to select cubes 
representing the whole charge, would be inaccurate if based simply 
on a compression test. 
An endeavor was made to compare the different cokes by approxi- 
mating the amount of breakage under conditions of present-day 
handling, showing the percentage of coke over 2-inch size that may be 
expected to reach the top of the charge in the blast furnace. Fifty 
pounds of each coke were selected, as nearly as possible representing 
the average size of the coke after handling at the ovens. This coke 
was dropped a distance of 6 feet onto a rigid (1-inch) iron plate. All 
pieces over 2 inches in size were weighed and again dropped, the 
operation being repeated three times. The results of these drop tests 
are shown in the detailed statement. 
The yield of coke appears to be increased and the amount of breeze 
reduced by preliminary crushing. Whether there is a limit to the 
degree of fineness, or whether a point may be reached beyond which 
finer crushing gives no appreciable improvement or has opposite 
effects, can not be determined from the present results ; but the data 
available indicate that it would be economical to crush all coal before 
charging into the ovens, even though a coke of good quality may be 
obtained without this preliminary treatment. Fine crushing also 
appears to increase the strength of the coke and make the fracture 
less irregular, by the greater uniformity and distribution of the ash, 
but the weight per cubic foot is reduced. The strength of the coke 
is probably influenced by the amount, composition, and distribution 
of the ash, but the results so far obtained show no definite relations 
between these factors or their relative importance. 
The matter of investigating the action of C0 2 on red-hot coke as 
determining its value for furnace work was thoroughly considered. 
