the Constitution of Carbon Compounds. 83 



Discussing a series of cases in this way, Thomsen arrives 

 at the mean values 2r— 30130 units ; 1^=14056 units. 



It will, however, be observed that the value of v l is prac- 

 tically identical with that previously found for v 2 ; whence it 

 follows that the same amount of heat is developed in the 

 combination of carbon atoms, whether they become singly or 

 doubly linked ; or, in other words, that there is no difference 

 between the two modes of union. 



The heat developed when carbon atoms become trebly 

 linked may be deduced from the heats of formation of ace- 

 tylene, CH : CH, allylene, CH 3 . C : CH, and dipropargyl, 

 CH i C . CH 2 . CH 2 . G : CH, viz. 28990, 74610, and 133080 

 units. Heat may be assumed to be developed in their for- 

 mation in the manner indicated in the following equations: — 



(2C,H 2 ) = 28990= 2r + v 3 , 

 (3C,2H„) = 74610 = 2. 2r + ^, 

 (6C, 3H 2 ) = 133080 = 3. 2r + 2v 3 + Sv v 



Substituting for 2r and i\ the mean values above given, three 

 values of v 3 are found, viz. —1140, 294, and 261 units. The 

 mean of these is —81 units, a value so small that it may be 

 neglected ; and it would therefore appear that the so-called 

 treble linking of carbon atoms is unattended with the deve- 

 lopment of heat. 



The data recorded by Thomsen afford, in his opinion, 

 abundant proof that^ a single carbon atom may retain two, 

 three, or four others w T ith the same degree of firmness as one. 

 The following Table contains several examples, the values of 

 v (=v 1 or v 2 ) being deduced by subtracting the heat due to 

 the combination of the hydrogen from the total heat of for- 

 mation, 30000 units being taken as the mean value of 2r : — 



Table IV. 



V. 



Methylmethane, CH 3 (CH 3 ) 104160- 90000= 14160= v 14160 



Dimethylmethane, CH 2 (CH 3 ) .. 148510-120000= 28510 = 2v 14255 



Trimethylmethane, CH(CH 3 ) 3 ".. 193690 - 150000 = 43690 = 3?; 14563 



Tetramethylmethane, C(CH 3 ) 4 . . 236850-180000= 56850 = 4v 14212 



Propylene, C,H 6 117200 - 90000 = 27200 = 2v 13600 



Benzene, C 6 H 6 216740 - 90000 = 126740 = 9v 140S2 



But the one hundred and twenty compounds burnt do not 

 afford a single instance from which it can be inferred that 

 two carbon atoms are ever held together by a force exceeding 

 that equivalent to about 14200 heat- units. 



Hence Thomsen concludes that one carbon atom cannot be 

 united to another by several affinities ; and that compounds in 

 which the carbon atoms are popularly supposed to be doubly 



