MAKViNE.l GEOLOGY ROCKS EAST OF FRONT RANGE LIGNITIC. Ill 



the moisture has been expelled. They consequently give too liigh per- 

 c^entages of volatile products, fixed carbon, and ash, as compared with 

 the other analyses : and in tliem, therefore, the percentages of these 

 ingredients should be diminished proportionally to the amount of water 

 present in each. 



A few words in connection with the heat-producing power of coals. 

 The amount of heat developed in the burning of coal is simply the result 

 or outward expression of the chemical union of the oxygen of the air 

 with those substances in the coal for which it has a chemical attraction 

 or affinity. These are principally the carbon and the hydrogen. The 

 products of the union of oxygen with these simple elements are the com- 

 pound substances carbonic acid and water. The amounts of these pro- 

 duced in combustion represent directly the amount of heat which has 

 been produced as the result of their formation. Having once been 

 formed, chemical action ceases and no further heat arises. If substances 

 are present in the original coal that are now combustible, or already 

 united with oxygen, that is, already burned, they deteriorate the coal 

 accordingly. The ash and moisture present in coals are such substances; 

 they both act as simple impurities, as slate or clay would act, diminish- 

 ing the relative percentages of the combustible ingredients, and hence 

 the heat-producing power of the whole. But the moisture acts further; 

 to convert it into steam requires a considerable amount of the heat pro- 

 duced by the other substances, and which would otherwise be available. 



The amount of moisture in the same coal may be a very variable 

 quantity; so that in analyses the moisture is often first driven off and 

 its amount determined, and the remaining ingredients calculated as per- 

 centages of the dried coal, as has been observed in those marked "^" in 

 the table. 



Practically, however, the moisture goes into the furnace with the coal, 

 there to absorb a large amount of heat and diminish the metallurgical 

 value of the coal as a fuel. Analyses which ignore it, therefore, give 

 misleading results. 



Are there no other ingredients present which would further deterio- 

 rate the coal f In the table above the "volatile products" are consid- 

 ered as combustible. Ultimate analyses, however, show them to be 

 composed of carbon, hydrogen, oxygen, and a small quantity of nitro- 

 gen. The latter is simply inert, an impurity, and too small in amount 

 to be of importance. But the oxygen is already united with the re- 

 maining two, and to just this extent they must be considered as already 

 burned, and so far unavailable as heat-producers. 



This oxygen is usually considered as being combined with the hydro- 

 gen to form water. From the " volatile products," then, there should 

 be taken away as nou-calorific the oxygen, and so much of the hydrogen 

 as with it will form water, leaving only the remaining hydrogen and all 

 the carbon as available for producing heat. This " combined water" in 

 the "volatile products" acts just as theuncombined water, or "moisture," 

 in diminishing the efficiency of the fuel. To arrive at its amount, ulti- 

 mate analyses only will serve the purpose. To illustrate these points, 

 Mr. Rossiter W. Eaymond, CTnited States commissioner of raining sta- 

 tistics, has recently* collected a number of ultimate analyses of lig- 

 nites, (none, however, I am sorry to say, of coals in my district,) some of 

 which I reproduce here, with two additional ones, following him in the 

 lessons he draws from them. 1 have also added columns 15 and 10, 

 which are explained later : 



* See Engineering and Mining Journal, May 27, 1873, Silliman's Journal, Sep- 

 tember. IBTo, p. 220, and Report of tije Commissioner of Mining Statistics for 1872, 



