Explosion of Hydrogen and Oxygen. Ill 



sufficiently small size to arrest explosion. Neither can it be sup- 

 posed that the outlet at the extremity of the jet was insufficient 

 for the expansion of the exploding mixture, and that in conse- 

 quence of that expansion, the inflamed gases were driven back 

 into the copper globe. This expansion must have been far 

 greater than 15 or 18 times, as deduced from Davy's experi- 

 ments, to have overcome the force exerted by the gases, which 

 at the moment were issuing from the globe, under a pressure 

 probably of nearly two atmospheres. 



The expansion of hydrogen and oxygen gases by explosion, 

 has not, I think, been satisfactorily determined ; and Davy, 

 whose results are most commonly adopted, does not appear to 

 have deemed his own conclusive. I have made some experiments 

 on the subject, and should not have offered the preceding re- 

 marks until more satisfactory results had been obtained, had it 

 not been necessary to defer the investigation to an interval of 

 more leisure. 



When water is mechanically suspended in the gases, the dan- 

 ger of retraction and explosion is undoubtedly increased, but the 

 influence of the small quantity formed in the jet on the occurrence 

 of the slight explosions already alluded to, must have been in a 

 great measure, if not altogether, counteracted by the elasticity of 

 the issuing gases. 



The cause of this explosion is certainly mysterious ; but in 

 whatever manner we may attempt to explain it, it must be re- 

 garded as additional evidence of the danger of employing the 

 gases in a state of previous mixture, and of the importance of 

 adhering to the use of two separate vessels and the concentric jet. 

 With these, although less convenient on some accounts, there are 

 other advantages ; their perfect safety, however, is alone suffi- 

 cient to induce us to recommend them, and them alone, to the 

 chemical student. 



The trials with the tube of Hemming previous to the occur- 

 rence of this explosion, seemed to warrant the statement in its 

 favor which has been made in a note in the edition of my Manual 

 of Chemistry, now passing through the press. 



Laboratory of Harvard University, Cambridge, June 5tli, 1839. 



