136 THE NEW WORLD OF SCIENCE 



while the usefulness of the nitro substitution compounds, both 

 those derived from aliphatic hydrocarbons as well as those from 

 aromatic hydrocarbons, and from many of their derivatives 

 as explosives per se was established. In fact Sprengel in 1873 

 stated that picric acid, a nitrosubstitution compound discov- 

 ered by Woulff in 1771, contains a sufficient amount of avail- 

 able oxygen to render it, without the help of foreign oxidizers, 

 a powerful explosive when fired with a detonator. As each 

 of the parent substances of these organic explosives was known 

 to be a member of a series yielding similar derivatives, most of 

 which through progressive substitution and isomerism would 

 each yield several nitric esters or nitrosubstitution compounds, 

 the number of actually known explosive compounds was very 

 large, while they were greatly exceeded in number by those 

 whose existence had been made evident but which had not, 

 for obvious reasons, such as their scarcity, cost, presence of 

 objectionable radicals, such as the haloids, been developed and 

 made use of. In addition many of these explosive compounds 

 were made use of as components of explosive mixtures, as 

 nitroglycerin was in a multitude of dynamites, or they were 

 modified physically, as nitrocellulose was when by colloidiza- 

 tion and induration of its grains it was converted into smoke- 

 less powder. Other oxidizing agents were also substituted 

 for potassium nitrate, such as other nitrates, chlorates, per- 

 chlorates, permanganates, dichromates, and liquid oxygen, and 

 other combustible agents for the charcoal, such as aluminum, 

 magnesium, hydrocarbons and cereals of various kinds. 



In 1870, as a consequence of the Franco-Prussian War, there 

 was formed a Scientific Committee for the Defense of Paris, 

 of which Berthelot was a member. He then directed and con- 

 ducted researches in explosives, which resulted in the accumu- 

 lation of the mass of information regarding these substances 

 which is set forth in his " Force des matieres explosive," and 

 in the creation, in 1878, of the permanent Commission on Ex- 

 plosive Substances, with Berthelot as Chairman, which has been 

 intensively engaged in researches in explosives ever since. 



