64 DURATION OF EXPLOSIVE REACTIONS. 



These combustions, started by a small flame in a test tube, are 

 gradual and progressive, and only produce very feeble explosions 

 like that of carbonic oxide and oxygen. 



By means of a powerful electric spark combustion also takes 

 place, and with singular violence, which shows the difference in 

 the mode of propagation of the chemical action. 



Here it may be mentioned that phosphorus burns briskly in 

 nitric oxide, that the same takes place with boiling sulphur, 

 with carbon previously made incandescent, and that carbon 

 bisulphide also burns briskly in this gas ; these are well-known 

 experiments. 



11. The principal cause of these diversities is the difference 

 in the temperatures developed by the combustible bodies burning 

 at the expense of the nitric oxide. 



The theoretical calculation of these temperatures may be made 

 by admitting, in the ordinary way, that the specific heat of a 

 compound gas is equal to the sum of its elements, and that each 

 of the latter taken at its molecular weight possesses the same 

 specific heat as hydrogen, that is, 6 '8 for H 2 = 2 grms. at 

 constant pressure. Temperatures thus calculated are certainly 

 not the real temperatures, yet it may be admitted that the order 

 of relative amounts is the same, and that is sufficient for our 

 comparisons. 



Mixtures which do not ignite. 



Theoretical temperature 

 of combustion. 



NO + H 2 (water, gaseous) 5900 



NO + CO ,. 6600 



3NO + CH 3 C1 (water, gaseous) 5700 



4NO + CH 4 (water, gaseous) 6300 



6NO + (CH 8 ) 2 (water, gaseous) 6000 



2NO + S taken at 15 6600 



Mixtures which do ignite. 



Theoretical temperature 

 of combustion. 



2NO + CN ... ... 8500 



5NO + C 2 H 2 (water, gaseous) 8700 



6NO + C 2 H 4 (water, gaseous) 7400 



6NO + CS 2 ... 7500 



2NO + C ... 8200 



5NO + P 2 10200 



4NO + PH 3 8400 



2NO -j- S previously heated to 450 ... 7050 



It will" be observed that the theoretical temperature of 

 combustion of sulphur, taken at about 15 by nitric oxide, is 

 very near the limit ; it therefore does not burn. On the contrary, 

 if the sulphur be contained in a heated receptacle and kept at 

 a temperature of about 450 by boiling, the nitric oxide being 

 rapidly raised by contact with the vessel to about the same 

 temperature, and thus the temperature of combustion of the 



