March 10, 3899.] 



SCIENCE. 



361 



their deliberations is the establishment at 

 Woolwich, England, of a station for testing 

 all explosives offered for use in coal mines, 

 and hei-eafter no explosives but those which 

 successfully pass these tests can be used, 

 and then only in the manner minutely de- 

 scribed in governmental authorization.* 



The closer study of the phenomena of 

 explosions in gases, consequent on these in- 

 vestigations, has developed many interest- 

 ing facts. Bunsen found that when mix- 

 tures of hydrogen and oxygen and of carbon 

 monoxide and oxygen in equivalent pro- 

 portions were inflamed the union went on 

 by fits and starts, and that the velocity of 

 propagation of the reaction, through nar- 

 row orifices, was 34 meters per second in 

 the hydrogen-oxygen mixture, and but one 

 meter per second in the carbon monoxide- 

 oxygen mixture, t Mallard tested various 

 mixtures of methane and air, and coal gas 

 and air, in the same way finding the ve- 

 locity of combustion to diminish rapidly as 

 the proportion of inert gases present in- 

 creased, and obtaining a maximum speed in 

 the case of eight volumes of air to one vol- 

 ume of marsh gas of 0. 56 meters per second. % 



Berthelot, using tubes of 40 meters in 

 length and 5 millimeters in diameter, ob- 

 tained velocities of 2,810 meters per second 

 for hydrogen-oxygen, 1,089 for carbon 

 monoxide-oxj'gen and 2,287 for me- 

 thane-oxygen, § and found that the reac- 

 tion could be propagated in three dif- 

 ferent ways : First, by combustion, as 

 observed by Bunsen, in which the heat 

 evolved is being continually lost through 

 radiation and conduction, and in which, con- 

 sequently, the pressure is exerted by the 

 layer of burning molecules on their adjacent 

 molecules, and hence their velocity of trans- 



* Kept. Com. to inquire into the History of Ex- 

 plosives for Use in Coal Mines, London, 1897. 

 t Ann. Chim. Phys. (4) 14, 449. 

 % Ann de Mines 8, 187 1. 

 I Sur la force de la poudre, 1, 153. 



lation tends constantly toward a minimum. 

 Second, by detonation in which the heat 

 evolved, the pressure produced by the re- 

 acting molecules on contiguous molecules, 

 and the velocity of translation of the ex- ' 

 plosive reaction all tend toward the max- 

 imum. And, finally, an intermediate stage ; 

 all three being marked by distinct waves. 

 Von Octtinger and von Gernet * have, by a 

 very ingenious arrangement, succeeded in 

 photographing, first, a fundamental one, 

 which they style Berthelot' s wave ; second, 

 more or less paiullel secondary waves, 

 whose existence they explain on Bunsen' s 

 hjqjothesis of the reflex action of waves due 

 to successive explosions produced by the 

 electric spark, and which they style Bun- 

 sen's waves ; and third, polygonal waves of 

 smaller amplitude. They obtained a veloc- 

 ity of 2,800 meters per second, which is of 

 the same magnitude as those obtained by 

 Berthelot. 



Berthelot and Vieille's experiments show 

 that when an explosion occvirs in a gaseous 

 mixture a number of ignited molecules are 

 projected /forward Avith a velocity corre- 

 sponding with the maximum temperature 

 produced by the chemical combination. 

 The impact of these molecules causes the 

 ignition of the adjacent particles, and the 

 rate of progression of the combustion is 

 thus dependent upon the activity of the 

 chemical action. 



Mallard and Le Chatelier find that the 

 rate of propagation of flame through an in- 

 flammable gaseous mixture is aiiected not 

 only by the temperature and size of the 

 igniting flame, but also by the mechanical 

 agitation or disturbance of the mixture it- 

 self. These results are not surprising when 

 it is considered that for the spread of com- 

 bustion in an inflammable gaseous mixture 

 it is necessary that the temperatui-e of the 

 combustion should be suflicient to ignite the 

 uninflamed portion. 



* Ann. der Phys. 



