346 cox. 



the Coinansi mine at Danao, Cebu (test 1?) where there was an abnormal 

 waste to the stack and the efficiency recorded is therefore probably 

 somewhat low. 



It has been shown ^^ that any considerable percentage of carbon mon- 

 oxide is threatening to efficiency. Owing to the infiltration of an 

 unknown quantity of air no exact limit could be set to this, but since the 

 presence of carbon monoxide may also be talien as an indication of other 

 incomplete combustion losses, high carbon monoxide is a prominent 

 danger signal. It has also been shown ^'^ that the furnace efficiency drops 

 very rapidly after the carbon dioxide content in the ilue gases has 

 reached about 9 per cent or perhaps 13 per cent if the gas has not been 

 diluted by leaks. Prom a knowledge of the law of mass action one 

 would expect, where the oxygen content is low and the carbon dioxide 

 high, that some carbon would only be partially oxidized, that is, the 

 presence of some carbon monoxide would be probable ; however, an equi- 

 librium may not always be attained in the combustion chamber. As the 

 flue gases passed the sampler in the seventeenth test the oxygen content 

 •was higher and carbon dioxide lower than in the tenth where combustion 

 was complete. Such a condition as that in the seventeenth, where the gas 

 analyses represent the average of a period, might be produced by careless 

 stoking so spasmodic that at times the percentage of ox3'gen would be 

 small, with incomplete combustion, and at other times so large, that the 

 average oxygen content would be increased. However, I do not believe 

 that this is the case in this series. An explanation which suggests itself 

 is that each individual coal, at any given temperature, may require a 

 certain excess of oxygen, varying with the complexity of the hydrocarbon 

 compounds, to eifect complete decomposition of the coal gases. If the 

 latter pass the high temperature of the furnace undecomposed, then the 

 small supply of oxygen is not sufficient to effect combustion before they 

 escape from the combustion chamber. 



Furthermore, owing to the coolness of the fuel bed and combustion 

 chamber when highly volatile coals are burned, combustion takes place 

 slowly and it is not surprising that the carbon monoxide and other 

 combustible gases are swept on and cooled below their ignition tempera- 

 tures before combustion is complete. 



The corrected ignition temperatures of various molecular relations of hydrogen 

 and carbon monoxide, with oxygen are the following :^^ 



4H,+O,=605° 6CO-fO,=721° 



2H,+O:=540° 4CO+0,=628'' 



H,+0.=514° 2CO-fO„=601° 



H,+2O:=530° CO+0,=631° 

 H,+40,=571° 



^"V. S. G. 8. Bull. (1907), 325, 65. 



" Ihid. 51. 



'«K. G. Falk, Ann. d. Phys. (1907) (4), 24, 450. 



