coal. 439 



of moisture, that would be one hundred pounds in every ton that might be 

 occupied by combustible material, and then it would take as much more to 

 drive out the moisture, so at least two hundred pounds out of every ton 

 would be unavailable on account of that percentage of water. 



The greater percentage of ash a coal contains the less valuable does it be- 

 come. The more fixed carbon a coal contains the greater its commercial 

 value. The more volatile combustible material of a certain character a coal 

 has the greater is its value, at least to a limited extent. 



COKE. 



A coal is increased in value by having good coking qualities. Coke is the 

 solid portion of the coal after the volatile matter has been driven off. The 

 coke retains the carbon and ash of the coal, so that a coal that has a high 

 percentage of ash and volatile matter will be poor in carbon and in the coke 

 it produces. The coal loses none of its bulk in the process of coking, but 

 loses considerable in weight — at least one-half. The bulk of coke varies with 

 the method of obtaining it. 



Each kind of coal should be treated in making coke according to its own 

 peculiarities. A coal that will give a good coke under one system of treat- 

 ment might give a poor quality of coke under a different treatment. It is 

 never advisable to send a coal away to some distant place to be tested in a coking 

 furnace where they have been coking an entirely different coal. The result 

 is very seldom satisfactory. The better plan is to build a small coking fur- 

 nace at the mines and make the test in several different ways in order to get 

 the best results. A small furnace could be built for a few hundred dollars, 

 and the proprietors of the mines could have the work done by their own 

 men, and let the coal be treated according to its own peculiarities, and not 

 by some one whose interest might be subserved by producing a poor quality 

 of coke in the test. 



Tests as to the coking quality of a coal made in a laboratory are never sat- 

 isfactory, because by rapid heating the small quantities used for analysis a 

 much larger proportion of volatile matter may be driven off than by the 

 slower process used in coking coal in a large way. 



The principal object in coking, outside of concentrating its carbon and pre- 

 venting its becoming pasty in the furnace, is to free the coal from sulphur, as 

 the sulphur ruins the malleability of the iron. 



So far as laboratory tests can determine, the coals of Texas have good cok- 

 ing qualities, and tests of the coal for coking purposes made in ovens where 

 other coals are being coked have proven only partially satisfactory. The body 

 of the coke was good enough, but the sulphur it retained was too high. This 

 could be remedied by different treatment in the coking ovens. If the coal is 



