34 



THE STOCKFEEDER'S COMPANION 



For complete oxidation of two molecules of carbo- 

 hydrate (starch) as compared with two molecules of fat 

 (stearin) the formulae given below will show how much 

 oxygen would be required : 



I2CO 2 + 



gives Carbon dioxide and 



ii4CO 2 



gives 



Carbon dioxide and 

 gas 



ioH 2 O 



Water 



noH 2 O 



Water 



It is now necessary to take into account that the 

 fat molecule is over nine times as heavy as the starch 

 molecule, and the simplest way will be to calculate 

 what weight of oxygen is required in each case to 

 combine* with (oxidise) I Ib. of carbohydrate and fat 

 respectively. Taking the atomic weights: carbon 12, 

 hydrogen I, and oxygen 16, we find that : 



(a) 324 Ibs. starch require 384 Ibs. oxygen for complete oxidation, 

 i ID. 55 11 IDS. 11 11 11 



i Ib. 



3 2 4 

 1-185 



(b) 1780 Ibs. stearin require 5216 Ibs. oxygen for complete 



[oxidation. 



i Ib. 



2-930 Ibs. 



Hence, by dividing (a) into (b) we find that stearin 

 (fat) is 2-472 times as valuable for heat production 

 as starch (carbohydrate). This value, however, varies 

 with every different kind of fat, and it is usual to 



