the Constitution of Carbon Compounds, 101 



Nitromethane, 55820 3r = 45000 10820 



Nitroethane . 101900 5r + 2v = 89200 12700 



The mean value of P — R is thus 11760 units: deducting from 

 this the heat developed on combination of a carbon and a 

 nitrogen atom by a single affinity, 2600 units, the remainder, 

 9160 units, is the heat developed in the formation of nitrogen 

 dioxide; but this has previously been stated to be —8415 

 units (§ 14) . So that the value deduced from the two nitro- 

 compounds under consideration differs to the extent of 17575 

 units from that determined experimentally by means of nitric 

 peroxide. This result is again suggestive of a constitution 

 different from that commonly attributed to the nitroparaffins. 

 Thomsen points out that by formulating them as nitroso- 

 alcohols, heats of formation may be deduced which agree with 

 those found ; thus : — 



Nitromethane = CH 2 (NO) .OH = 2r + C. OH + C.N + N.O 



= 55820 units. 

 Nitroethane = CH(CH 3 )(NO).OH =±r + v + C.OH + C.N + NO 



= 101900 units. 



Putting *•= 15000, w = 14200, C . OH=44520 (§ 10), and 

 O . N=2600 (§ 15), the heat of formation of NO will be— 



If calculated from Nitromethane, — 2 1300 units, 

 „ „ Nitroethane, —19420 „ 



These values differ but slightly from that found, viz. —21575 

 units. 



(19) Heat of Formation of Sulphur Compounds. — It will not 

 be necessary to discuss Thomsen's conclusions regarding these 

 compounds ; it will suffice to call attention to the one instance 

 in which he arrives at a result at variance with received 

 opinion. This is in the case of thiophen, which is usually 

 represented bv the formula 



CH=CH 



S< I • 



\CH=CH 



On grounds similar to those advanced in the case of benzene 

 and pyridine, Thomsen concludes, however, that the carbon 

 atoms cannot be doubly linked, but that they are united by 

 five single bonds, and that the sulphur atom is united to a 

 single carbon atom by two affinities, as shown by the formula 



/OH\ 



S=C< I >CH 2 . 

 X CH/ 



