MEGA8S AS FUEL. 



as the cellulose, it is possible to calculate the thermal value of a megass ; thus, 

 a megass of composition fibre, 42 per cent., sugar, 9-666 per cent., will afford, 

 on complete combustion, -42 X 7533 + -0966 X 7120 = 3851 B.T.U. per Ib. 

 for the fibre and sugar alone, to which must be added that due to the glucose 

 and other organic matter ; if this be taken as y 1 ^ that due to the sugar, the 

 gross thermal value of the megass will be 3920 B.T.U., and per unit of dry 

 matter, supposing the megass contains 47 per cent, of water, 7396 B.T.U. 

 The heat of combustion of megass of different origin has been experimentally 

 determined by a number of workers. Geerligs 4 , whose results are discussed 

 more fully in another section, found the heat of combustion, per Ib. of dry 

 matter, to be sensibly constant ; his extreme values in B.T.U. are 8249 and 

 8514, with a mean of 8381 ; Burwell 5 , in Louisiana, obtained a mean value of 

 8325, with extremes of 8289 and 8384. These values are considerably higher 

 than would be obtained on calculation on the lines exemplified above ; actually, 

 then, it will be sufficient, under average conditions, to accept a fixed value of 

 8350 B.T.U. per Ib. of dry matter in a megass. 



Products of Combustion of a Megass. Each pound of carbon 

 on combustion requires a theoretical minimum of 2-67 Ibs. oxygen, a quantity 

 supplied by 12-03 Ibs. of air, the remainder, 9-36 Ibs., being nearly all nitrogen ; 

 at a temperature of 84 F. this quantity of air occupies 165 cubic feet. The 

 combustible elements in megass contain hydrogen and oxygen in the same pro- 

 portion that they exist in water, so that in calculating the air required for 

 combustion only the carbon need be taken into account. Of the bodies 

 present in megass, cellulose contains 44*4 per cent., xylan 45'4 per cent., 

 sugar 42-1 per cent., and glucose 40-0 per cent, of carbon, so that from the 

 analysis of a megass its carbon content can be found. In actual determinations 

 Geerligs found megass to contain from 46 82 per cent, to 4 8 -45 per cent. 

 carbon, and from 6'30 per cent, to 6- 67 per cent, hydrogen on the dry ash free 

 material ; as an average then, per Ib. of dry matter, a megass may be taken 

 as containing 46-5 per cent, of carbon, and 6-5 per cent, of hydrogen, allowing 

 that the dry matter contains 2 per cent, of ash. 



Per Ib. of dry matter, then, the products of combustion of a megass will be 

 Due to carbon '465 X -7-= 1*705 Ibs. carbon dioxide. 



1 8 

 Due to hydrogen -065X--= '585 Ibs. water. 



Due to nitrogen of air . . -465 X 9*36= 4 '352 Ibs. nitrogen. 



Fuel Value of Megass as influenced by Variety. In 



" Sugar and the Sugar Cane" (page 280) it was stated that it was a matter of 

 clinical observation that the megass from different varieties of canes exhibited 

 very different values as fuel, and that this difference could not be accounted for by 

 low fibre content of the cane or yet from the analysis of the megass. Similar 



411 



