PKOGEESS IN EXPLOSIVES GUTTMANK. 269 



Other metals might have a similar or even a better effect than 

 aluminum. Thus in 1900 already Desire Korda, of Paris, and the 

 author have considered the possibility of using- ferro-silicon. In 

 addition to the above-mentioned metals, the use of iron, silicon, silicon 

 carbide, zinc and its alloys, copper, and also the rare metals has been 

 patented. 



In his patent of 1871 on the explosives bearing his name," Prof. 

 Hermann Sprengel, F. E. S., said, seemingly without reference to 

 the rest of the patent, " I also employ picric acid," but in his famous 

 lecture delivered in 1873 before the Chemical Society he said dis- 

 tinctly : " Be it noticed here that picric acid alone contains a suffi- 

 cient amount of available oxygen to render it, without the help of 

 foreign oxidizers, a powerful explosive, when fired by a detonator. 

 Its explosion is almost unaccompanied by smoke." As a matter of 

 fact, Sprengel did fire some shots with picric acid at Messrs. John 

 Hall & Sons' factory in Faversham in 1871, but was not encouraged 

 by the service to pursue his experiments. 



Nothing further was heard of picric acid until 188G, when, as men- 

 tioned before, Eugene Turpin, of Paris, showed how to compress or 

 melt it for use in shells. The French service used picric acid, mixed 

 with collodion to give it greater density, under the name of melinite. 

 Later on it w^as compressed, but ordinary detonators failed to explode 

 it with safety, and the expedient devised by Alberts and the author 

 to use a primer of dry gun cotton was too inconvenient. The picric 

 acid has therefore to be melted, in which state it can be more readily 

 exploded by detonators, and has a density of about 1.65. Picric acid 

 melts at 122.5° C, and must therefore be either heated in an oil bath 

 by high-pressure steam or in a special " stove." Melting it at such a 

 high temperature is very inconvenient and is not without danger, 

 hence use was made of the well-known phenomenon that a mixture 

 of two substances of high melting points has nearly always a lower 

 melting point than that of either of its constituents. Girard ^ has 

 given a long list of the melting points of explosive mixtures of this 

 kind. 



Almost every country has adopted picric acid as a disruptive agent, 

 under a different name, and differences in composition consist merely 

 in the addition of an ingredient to reduce the melting point. Such 

 additions are nitronaphthalene, camphor, dinitrotoluene, etc., and 

 the names are melinite, lyddite, pertite, shimose powder, picrinit, 

 ecrasit, etc. 



Besides having a high melting point, picric acid is inconvenient 

 in other ways. Left in contact with metals or oxides it forms very 

 dangerous picrates, hence the necessity of varnishing the interior of 



« British patent No. 2042, of 1871. 

 6 Id., No. 6045, of 1905. 



