374 TRANS. ST. LOUIS ACAD. SCIENCE. 



tion was thoroughly pui'ified by passing- through several towers 

 of sulphuric acid and lime before reaching the combustible. 



The reaction for Cyanogen was very pronounced : a splendid 

 precipitate of prussian blue was obtained quite easily. The time 

 of combustion of the 50 litres of Marsh gas was little over an 

 hour. In this experiment we have positively the answer to our 

 inquiry, ^'whether atmospheric Nitrogen plays a role chemically 

 in the combustion of Carbon compounds?" All inducing agents 

 for formation of Cyanogen were scrupulously excluded. 



We conclude, then, that nitrogen of the atmosphere takes part 

 chemically, generally, in the combustion of carbon compounds 

 forming transiently Cyanogen or Hydrocyanic acid. In other 

 words, we affirm with Morren that Carbon and Nitrogen can 

 unite directly at very high temperatures. Together with a great 

 preponderance of exothermic compounds, we have formed an en- 

 dothermic compound. This is the general rule in the formation 

 of endothermic compounds. I mention only the formation of 

 Chlorate of Potash. 



The reason of the formation of this endothermic compound in 

 the case of combustion may, I think, be found in the most pro- 

 bable fact that we have atoms and not molecules reacting upon 

 one another. When the compound is broken up, there is a cer- 

 tain time when carbon must be in the nascent or atomic state. 

 What its affinities are there we may judge from analogy. It is 

 not impossible that the formation of cyanogen is under such cir- 

 cumstances really exotheimic. The heat of dissociation of the 

 carbon molecule is, according to Thomsen, 39610 calorics; so- 

 that we see that atomic carbon forming cyanogen would cause 

 an evolution of about 9000 calorics, and would under the cir- 

 cumstances be exothermic. 



We may presume, also, that in Morren's experiment the mole, 

 cules of carbon and nitrogen are dissociated previous to actual 

 combination. 



