82 Prof. H. E. Armstrong on the Determination of 



fore, differ by v 2 , i.e. 14250 units (§4). The difference 

 73470-14250 = 59220 units is the heat developed in the 

 combination of two atoms of carbon with two molecules of 

 hydrogen ; while the heat of formation of methane — 59550 

 units — is that developed in the union of the same quantity of 

 hydrogen with a single atom of carbon. The two values may 

 be regarded as identical ; and hence, argues Thomsen, it may 

 be concluded that the four atoms of hydrogen are equally 

 firmly held, whether they are associated with a single or with 

 two carbon atoms ** 



Halving the numbers 59220 and 59550, we have 29610 

 and 29775 units as the heat developed in the combination 

 of a gram- molecular proportion of hydrogen with gaseous 

 atomic carbon. The value 29775 is denoted by Thomsen by 

 the symbol 2?\ 



(7) Heat developed in the Combination of Carbon Atoms by 

 single, double and treble Affinities. — The amounts of heat 

 developed in the combination of (gram-atomic proportions of) 

 carbon atoms by one, two, and three " affinities " of each, i. e. 

 in the manner in which they are assumed to be associated in 

 the paraffins, in ethylene, and in acetylene respectively, may 

 be designated by the symbols v ly v 2 , r 3 . 



It has been previously shown that v 2 = 14250 units. 



As regards the value of v 1? the heat developed in the 

 formation of ethane, C 2 H 6 , results from the combination 

 of three hydrogen molecules with two carbon atoms, and 

 of these carbon atoms with each other by single affinities ; 

 hence * 



(2C,3H 2 )=3 . 2r + r 1 = 104160 units. 



.-. ^=104160-89325 = 14835 units. 



Or, comparing ethane with benzene, and assuming that there 

 is one single linkage between carbon atoms in the former and 

 nine such in the latter (§ 8), 



(6C, 3H 2 ) =216740 = 3 . 2r+9v, 

 (2C,3H 2 ) =104160 = 3. 2r + v l9 



.-. 8^ = 216740-104160 = 112580 units. 



.-. v 1 = 14073 and 2r = 30029. 



* It should be noted, however, that the difference between the heats 

 of formation of methane and ethylene is the value v 2 ; and that the 

 heat of formation being dependent on/. C„ as/. C T and v 2 are both given 

 by the same equation, the calculated and found differences must be 

 identical ; Thomsen's conclusion as regards the relation of the hydrogen 

 atoms in ethylene to the two carbon atoms must, therefore, be held to be 

 "not proven." 



