224 Intelligence and Miscellaneous Articles. 



These circumstances explain, on the one hand, why in the above- 

 mentioned caloriinetric measurements no peroxide of hydrogen 

 could be demonstrated (for in the slow combustion no more appears 

 to have been formed than was necessitated by the minute quantity 

 of sulphurous acid contained in the gases), aud, on the other, why 

 the amount of sulphuric acid contained in the water was so small ; 

 it appears to have arrived in the combustion-space not as sulphuric, 

 but as sulphurous acid. 



The same circumstances seem also to explain the green edge 

 shown by the hydrogen-flame when iodine is present. The simul- 

 taneous formation of iodic acid, which has been pointed out by Gr. 

 Salet*, may probably be connected with the occurrence of peroxide 

 of hydrogen. 



After these facts it appeared probable that in the third case of 

 the combustion also, viz. during the explosion of oxy hydrogen, 

 besides water, peroxide of hydrogen is produced, which supposition 

 was confirmed by experiment. It could be demonstrated in all the 

 experiments made in relation thereto : a scarcely perceptible quan- 

 tity of the water formed in the explosion gave the iodine reaction ; 

 and a drop was sufficient to show strikingly the perchromic-acid 

 reaction. 



During explosion the peroxide of hydrogen appears to be formed 

 in still larger quantity than in ordinary combustion ; but I have 

 not yet succeeded in carrying out a reliable quantitative determina- 

 tion, because all the tubes employed, of the length of about 1 metre, 

 were shattered. These unsuccessful experiments, however, led to 

 an in other respects interesting result : — All the tubes were very 

 strong, so that one of the weakest required a continued pressure of 

 100 atmospheres to burst it. To this must be added that it was 

 always only the part most distant from the place of ignition that 

 was burst, even when, with 3 millim. thickness of wall, its bore 

 was only 3-4 millim. in diameter — whence it follows that very pure 

 oxyhydrogen, such as I employed, occasions in long tubes, in the 

 part furthest from the place of ignition, a pressure of hitherto un- 

 suspected magnitude. This holds good even when the tubes are 

 narrowed by one or two coils of cord to 2 millim. internal diameter ; 

 but a slight content of air modifies the result considerably. I 

 believe that this can be accounted for as follows : — In consequence 

 of the considerable pressure arising at the place of ignition, the still 

 unburnt gas is driven with great velocity along the tube ; hence 

 the slowly spreading ignition meets continually with more and 

 more powerfully compressed gas ; wherefore the pressure in the 

 corresponding part of the tube inci'eases more and more, till finally, 

 at the end of the tube, the most violent action takes place. In my 

 experiments the pressure there was much greater than it can have 

 been, according to Bunsenf, in the most favourable case of simul- 

 taneous ignition of the entire mixture. 



* Conqrfes Rendus tie V Academic' des Sciences, lxxx. p. 884 (1875). 

 t Bunsen, Gasometrische Methoden, (1875) p. 256; cf. (1877) p. 331. 



