308 Mixier — Products of the Explosion of Acetylene. 



of acetylene is 1000 meters and higher per second,"- and in the 

 iron U-tube the expanding gas must move a column of mer- 

 cury about 80 cm in length, that is, the pressure on I 8q cm must 

 move one kilo of mercury. It is highly improbable that this mass 

 is displaced materially before the explosion is completed. If this 

 assumption be correct, the temperature at the instant of explo- 

 sion is the same in the U-tube as in the bomb. In the former 

 the expanding gas cools more rapidly than in the latter. In 

 the bomb there is a sufficient number of collisions to impart to 

 the molecules of nitrogen the energy adequate for combina- 

 tion or to dissociate them into atoms. In the U-tube the 

 volume of the gas increases after the explosion and the col- 

 lisions are fewer than in the bomb and the nitrogen does not 

 combine. Thus we may conclude that, even at the temperature 

 of exploding acetylene, a sufficient frequency of collisions is 

 requisite to cause nitrogen to combine. 



The amount of hydrocyanic acid remaining in the bomb 

 does not appear to depend upon the proportion of nitrogen in 

 the mixture exploded, for the result was the same with 15 per 

 cent of nitrogen in the mixed gases at a pressure of 4 atmos- 

 pheres as with 28 per cent at 5 atmospheres. It may be that 

 a fixed quantity of hydrocyanic acid per unit of space remains 

 when the products of the explosion cool and assume a state of 

 equilibrium. 



Acetylene and ammonia, as shown by experiments 49 and 50, 

 yield hydrocyanic acid at a much lower temperature than is 

 required to cause nitrogen to combine. It may be that 

 ammonia is the first compound of nitrogen formed in the bomb, 

 but the fact that a little ammonia is found in the products of 

 an explosion is not conclusive, as this may have resulted from the 

 decomposition of hydrocyanic acid. Dewarf passed a mixture 

 of hydrogen and nitrogen through a carbon tube heated 

 externally by an electric arc and obtained hydrocyanic acid. 

 Here the conditions were similar to those in bomb, namely, 

 carbon, hydrogen and nitrogen at a very high temperature. 

 Dewar made no statement regarding the presence or absence 

 of ammonia in the products of his experiment, and Berthellot^; 

 considered that ammonia played no part in the synthesis of 

 hydrocyanic acid effected by sparking a mixture of acetylene and 

 nitrogen. The results in the bomb indicate that less acetylene 

 remains when nitrogen is present than when pure acetylene is 

 exploded, but they are not conclusive. Berthellot (loc. cit.) 



*Bert"hellot and Chatelier, Comptes Rendus, exxix, 427 ; Ann. China, et Phys., 

 xx, 15. 



f Proc. Roy. Soc, xxix, 188, and xxx, 85. 

 | Comptes Rendus, lxvii, 1141. 



