162 OXYGENATED COMPOUNDS OF NITROGEN. 



volume. This remark applies likewise to the combustion 

 of cyanogen by nitric oxide. 



2. Combustion of Cyanogen by Nitric Oxide. 



The explosion of the following gaseous mixture, CN + 2NO 

 = C0 2 + N 3 gave + 175-3 ; + 172-9 ; + 175-0 ; + 174-4 ; + 

 175 -3 ; the mean being 174-6 ; explosion at constant volume. 



The difference between this number and the figure + 130-9 

 obtained with free oxygen under the same conditions, viz. the 

 value -|- 43*7, represents the heat liberated by the decomposition 

 of 2NO into its elements. According to these two data, the 

 union of nitrogen with oxygen to form nitric oxide (NO 

 30 grms.), N + = NO absorbs - 21-8 Cal. 



3. Combustion of Ethylene Try free Oxygen and Nitric Oxide. 



Similar experiments were made with ethylene, and yielded 

 the same results. It is, therefore, unnecessary to enter into 

 details. It will be sufficient to state that the difference between 

 the numbers observed corresponding to the union of the elements 

 nitrogen and oxygen N -f = NO, was - 21 -6 Cal. 



3. HEAT OF FORMATION OF NITROGEN MONOXIDE. 



The heat of formation of nitrogen monoxide was measured by 

 exploding carbonic oxide mixed first with this gas and then 

 with oxygen and taking the difference of the two results. 



1. Combustion of Carbonic Oxide by Oxygen. 



CO (14 grms.) +0 = CO* liberated + 33'7 and + 34'4. The 

 mean, + 34'0, refers to the explosion at constant volume. 



From this we pass to the heat of the combustion at constant 

 pressure 1 by adding 0'14, by reason of the condensation which 

 reduces 1 J vols. of the explosive mixture to 1 vol. ; we thus 

 obtain 3414 cals. This figure agrees almost exactly with that 

 previously obtained by the combustion of a jet of carbonic oxide 

 in oxygen, viz. + 34-09. 2 It also agrees with the value obtained 

 by the wet process 3 with formic acid, by oxidizing on one hand 

 the formic acid, and on the other hand transforming it into 

 water and "carbonic oxide. By this method the combustion of 

 carbonic oxide gave -f 34'25. 



2. Combustion of Carbonic Oxide by Nitrogen Monoxide. 

 CO + N 2 0, 22 grms. = C0 2 + N 2 liberated ; + 44'0 ; -f 451 ; 

 -f- 441, the mean being 44"4 ; explosion at constant volume. 



1 " Essai de Me*canique Chimique," torn. i. p. 115. 



2 " Annales de Chimie et de Physique," 5" seVie, torn. xiii. p. 13. 



3 Same collection, torn. v. p. 316. 



