INDIRECT CALORIMETRY 2!) 



the amount of C and O, which corresponds to each gram of 

 urinary nitrogen, one could, from the nitrogen excreted, calculate 

 the heat liberated from the protein of the diet. (1 gram of 

 urinary nitrogen = 26-51 cals.). Having deducted the protein Go 

 from the total O^ absorbed and the protein COg from the total 

 CO2 eliminated, one arrives at the figures corresponding to the 

 non-protein O^ and COg respectively. 



(VI) Now, as we have said, carbohydrates differ from fats in 

 their respective contents of C and O2. Carbohydrates have the 

 general formula ^-'(CHgO), while fats contain less O^ compared 

 with their content of oxidisable matter, e.g. CjgHgeOg. There- 

 fore, when carbohydrates alone are used, the ratio of the volume 

 of CO2 eliminated to the volume of O absorbed will be 1, as may 

 be deduced from the equation : 



C(H20) + O2 = CO2 + H2O ^^^ ^Q ^ 



1 vol = 1 vol R.Q = -^r^Trr =7 = 1- 



Vol (Jo 1 



Fats are compounds of glycerol, the trihydric alcohol, with organic 

 acids of the aliphatic (fatty) homologous series. The simplest 

 fatty acid is formic, H-COOH. The higher acids are built up 

 by successive additions of CHg. 



TABLE III 



Saturated Series. C^^Hg^Oa- 

 E.g. HCOOH— formic acid CH2O2 



CH3COOH— acetic acid C2H4d2 

 CHa-CHa-COOH— propionic acid Q^H^O^ 

 CH3CH2CH2COOH— butyric acid C4H8O2 



• •••••» 



CH3-(CH2)i4COOH— palmitic acid C16H32O2 

 CH3-(CH2)i5COOH — margaric acid C17H34O2 

 CH3-(CH2)i6COOH— stearic acid Ci8H3e02 



Unsaturated Series. C„H2„-202 



CH3(CH2)7CH = CH(CH2)7COOH— oleic acid Ci8H3,02 



A glance at this list will make it clear that the amount of 

 oxygen does not increase although the C and H are increased. 

 This paucity of oxygen content is more marked in the fats than 

 in the fatty acids. 



Palmitic Acid Glycerol Tri-palmitin 



CigHaiCOOi^HO 



Ci,H3iC0 0H HO-^CgHs = ^.i^.s^, + 3H2O 



C15H31CO OH H O^ 



