336 EREMACAUSIS OR DECAY 



gen is very rarely produced, and never when the 

 carbon is in excess. Kuhlmann found in his experi- 

 ments, that it was only when cyanogen was mixed 

 with an excess of oxygen gas, and conducted over 

 spongy platinum, that nitric acid was generated. 



Kuhlmann could not succeed in causing pure nitro- 

 gen to combine directly with oxygen, even under 

 the most favorable circumstances; thus, with the 

 aid of spongy platinum at different temperatures, no 

 union took place. 



The carbon in the cyanogen gas must, therefore, 

 have given rise to the combustion of the nitrogen by 

 induction. 



On the other hand we find that ammonia (a com- 

 pound of hydrogen and nitrogen) cannot be exposed 

 to the action of oxygen^ without the formation of an 

 oxide of nitrogen, and in con&equence the production 

 of nitric acid. ^ 



It is owing to the great facility w^ith which ammo- 

 nia is converted into nitric acid, that it is so difficult 

 to obtain a correct determination of the quantity of 

 nitrogen in a compound subjected to analysis, in 

 which it is either contained in the form of ammonia^ 

 or from which ammonia is formed by an elevation of 

 temperature. For when ammonia is passed over 

 red-hot oxide of copper, it is converted, either com- 

 pletely or partially, into binoxide of nitrogen. 



When ammoniacal gas is conducted over peroxide 

 of manganese or iron heated to redness, a large 

 quantity of nitrate of ammonia is obtained, if the 

 ammonia be in excess ; and the same decomposition 

 happens when ammonia and oxygen are together 

 passed over red-hot spongy platinum. 



It appears, therefore, that the combination of 

 oxygen with nitrogen occurs rarely during the com- 

 bustion of compounds of the latter element with 

 carbon, but that nitric acid is always a product when 

 ammonia is present in the substance exposed to 

 oxidation. 



The cause wherefore the nitrogen in ammonia 



