CHEMICAL CHANGES 117 



Hence 145*9 must be absorbed, while 158*4 must be evolved, 

 giving a balance of 12*4 units evolved. 



[The units are kilogramme-centigrade, and the substances 

 are taken in gramme-molecules.] 



Cellulose, 



CgHioOs + Hp = 3CO0 + 3CH4 



Heat of formation 246 68 291 49-5 



-^ If - — - ^ » 



Heat absorbed, 314. Heat evolved, 340'5. 



Evolution of heat, 26-5 units. 

 The heat of formation of cellulose is calculated thus : 



Complete combustion of 6C and loH to CO2 and water : 

 6C + 5H2 + O in excess = 6CO2 + 5H2O 

 6x97 5x68-4 



924 units. 

 Combustion of cellulose (CgHj^Oj) gives 678 units (Stohmann). 

 924 - 678 = 246. 



A Ihumin, 



Berthelot and Andr6^ state that i gramme of albumin dried 

 at 100° C. gives 5,691 calories (gramme-centigrade units). 



Hence CgHigNgOs = 185 of albumin give 185 x 5,691 = 

 1,052,835 = 1,053 kilogramme units. 



We must first calculate from this the heat of formation of 

 albumin : 



(8C + 13H + 2N + 3O) burnt = 8C02 + 6H20 + N2-hH 



8 X 97 6 X 68 

 776 + 408=1,184. 



Hence heat of formation = 1,184 - i>053 = i3i units.^ 

 Now, assuming a complete hydrolytic change : 



4C8Hi3N203+i4H20 = 4N2+i9CH4+i3C02-f4H 

 Thermally 4 X 1 3 1 14x68 19x16*5 13x97 



524 + 952 314-5 + 1,261 



1,476 absorbed. i575"5 evolved. 



Giving a balance of 1,576- 1,476= 100 units evolved. 



^ Chemical Society Abstracts, 1890, p. 937. 



"^ I have left out one hydrogen atom in this calculation, because in the enzyme 

 reaction one hydrogen per molecule of albumin is set free. 



