PROGBESS IN EXPLOSIVES — GUTTlvfANN. 289 



this theory by the fact that fulminate of mercury does not ordinarily 

 ignite fire damp, whilst black powder always does. The theory is, 

 however, controverted by certain black-powder mixtures, foremost 

 among which is bobbinite, which is safe up to a certain point, and by 

 nitrogh'cerin and blasting gelatin, which are not. 



The P^rench Government commission stated that an explosive 

 whose temperature of explosion was below 1,500° C. could be licensed 

 for use in fiery mines. Curiously enough carbonite, so far the safest 

 of all, and several others, which are licensed for such use, have a tem- 

 perature of explosion considerably higher than 1,500° C. 



Mr. Bichel, in conjunction with his collaborator. Doctor Mettegang, 

 says that the velocity of detonation, the maximum temperature of 

 the products of combustion, the length and the duration of the flame 

 of an explosive all influence the safety of an explosive adversely.*^ 

 He considers, and in the author's opinion very justly, the nature of 

 the products of combustion to be all important, whether they consist 

 of solid particles which remain incandescent for a considerable time, 

 or of large quantities of combustible gases shot forward with great 

 force. In this way he corroborates early attempts to photograph the 

 flame of an explosion made by Schoeneweg, the inventor of securite, 

 and by Siersch, of Pozsony. The velocity of detonation can not, how- 

 ever, be considered to be a determining factor under all circum- 

 stances. Certain nitroglycerin explosives, amongst which we may 

 also include carbonite, explode much mor-e rapidly than, say, bob- 

 binite, and yet show themselves to be much safer when tested. I 

 mj'Self have found that up to a certain point the addition of picric 

 acid gave increased safety on test. 



It will be remembered that the British commission found a water 

 jacket round the charge very efficient. Sodium carbonate, mag- 

 nesium sulphate, and other substances were tried, either separately 

 in front of the explosive or as ingredients. INIore prominence was 

 then given to the French recommendations, and the notion became 

 prevalent that the addition to the explosive must be a flame-cooling 

 agent in the shape of water vapor or some other heat-absorbing gas. 

 Thus permanganate, bichromate oxalates, and other salts were used, 

 and of late common salt has sprung into favor. 



The only definite result obtained so far is that ammonium nitrate 

 is absolutely safe in all quantities, and that cellulose and similar 

 substances in nitroglycerin compositions — e. g., rye flour in car- 

 bonites or wood pulp in other explosives — renders them highly inert 

 in fire-damp mixtures. Ammonium nitrate can not, however, be 

 used by itself, although Lobry de Bruyn succeeded in exploding it,^ 

 and therefore some combustible substance must be added. It simply 



« Gliickauf, 1904, No. 35. 



* Recueil cles travaux chimiques ties Pays-Bas, 1801, p. 127. 



