STATICS 117 



oxygen is required for the oxidation of the constituents of the 

 food. 



One hundred parts of protein contain 16 parts of nitrogen, 

 and 1 6 parts of nitrogen are equal to 34/3 parts of urea. 1 

 Therefore i part of protein yields 0*343 parts of urea. 



N 2 H 4 CO + 3 -> 2H 2 + C0 2 + N 2 

 60 parts of urea require 48 parts of oxygen. 

 Therefore 0-343 parts of urea require 0*27 parts of oxygen. 

 This amount is to be deducted from that previously calculated 

 for complete oxidation, giving [177 0*27] = 1-5 parts of 

 oxygen for each part of protein oxidised in the animal's body. 



It has been found by experiments in the respiration chamber 

 (p. 130) that about 0-03 parts of methane are formed from 

 each part of carbohydrate (starch). The corresponding amount 

 of oxygen is easily calculated. 



CH 4 + 2 O 2 -> CO 2 + 2H 2 O , ^ 



Sixteen parts of methane require 64 parts of oxygen, there- 

 fore 0-03 parts (equal to i part of carbohydrate) require 0-12 

 parts of oxygen ; to be deducted from the amount required for 

 complete oxidation, giving [ri2 0-12 =] ro parts of oxygen 

 required for each part of carbohydrate oxidised in the animal's 

 body. 



It appears, therefore, that each part of fat absorbed into 

 the animal's system can consume 2-9 times as much oxygen 

 as each part of carbohydrate, and each part of protein 1*5 

 'times as much oxygen as each part of carbohydrate. 



The investigations described above are cited by way of 

 explanation of what follows, rather than for the value of the 

 results as such. The potential energy does not correspond 

 exactly with the amount of oxygen required for oxidation. It 

 depends partly on the state of combination of the elements. 2 



1 N 2 H 4 CO = 28 + 4 + 12 + 16 = 60 



60 X 16 -T- 28 = 34-3 



2 The heat of combustion of isobutyl alcohol, (CH 3 ) 2 CH.CH 2 OH, is 

 661-5 Cal., and that of trimethyl carbinol, (CH 3 ) 3 COH, is 643-5 Cal. The 

 two substances are isomeric, i.e. they have the same percentage composition 

 and the same molecular weight ; the difference, 18 C., in the heats of 

 combustion is due to the way in which the atoms are combined. 



