Ik 



the Constitution of Carbon Compounds. 81 



combustion of this compound would exceed that of carbon 

 dioxide by 121090 units ; whence it follows,, the heat of com- 

 bustion of carbon dioxide being nil, that the heat of com- 

 bustion of the product in question should be 121090 units. 

 In point of fact, however, two molecules of carbon monoxide 

 are produced by assimilating an atom of carbon with a mole- 

 cule of carbon dioxide, the double linkage becoming annulled, 

 while at the same time the volume is doubled. In the act of 

 expansion 580 units are absorbed (§1): hence the heat of 

 combustion of the product of the union of an atom of carbon 

 with a molecule of carbon dioxide exceeds 121090 units by 

 the amount absorbed in the separation of " doubly-linked " 

 carbon atoms plus 580 units. The heat of combustion of 

 2 . CO is 135920 units ; therefore 



/. C 1 = 121090 + v 2 = 135920-580 = 135340 units. 



It being thus determined that 



f.G 1 = 135340 units, 



it follows that 



v 2 = 14250 units. 



(5) Heat absorbed in the production of Gaseous " Atomic " 

 Carbon. — The heat of combustion of gaseous " atomic " carbon 

 being 135340 units, while that of amorphous carbon is 96960 

 units, the amount of heat expended in passing from the 

 solid amorphous state to the gaseous atomic state will be 

 38380 units for each gram-atomic-proportion (12 grams). 

 The heat developed in the formation of a compound at con- 

 stant pressure from gaseous atomic carbon may hence be cal- 

 culated by adding for each atom of carbon in the molecule 

 38380 units to the uncorrected heat of formation (§ 1) cal- 

 culated for carbon in the amorphous state. All the heats 

 of formation subsequently to be given are deduced in this 

 manner. 



(6) Heat developed in the Combination of Hydrogen with 

 Carbon. — The heat of formation of methane, CH 4 , at constant 

 volume, calculated on the assumption that it results from the 

 combination of ordinary hydrogen with gaseous " atomic " 

 carbon — of two hydrogen molecules with one carbon atom — is 

 59550 units ; that of ethylene, C 2 H 4 , is 73470 units. Both 

 contain the same number of hydrogen atoms, but in the latter 

 there are two " doubly-linked " carbon atoms — assuming 

 ethylene to have the constitution popularly assigned to it : 

 the heat of formation of the two hydrocarbons should, there- 



