EXPLOSIVE AGENTS 321 



Poudre Barytique or Saxifraqine is of a similar character. It is the invention of a 

 Belgian officer, Captain Wynants, and consists of a mixture of charcoal and nitrate of 

 baryta, with a small proportion of saltpetre. The baryta-powder is comparatively 

 very slow burning ; and its special characters are such that its application could not 

 but remain limited to ordinary mining and quarrying uses. 



Picric Acid or Carbazotic Acid. Among the numerous products obtained by the 

 action of nitric acid upon materials of organic origin, one of the earliest discovered 

 possessing explosive properties is the product known as picric acid, which is furnished 

 in that way by indigo, &c. Picric acid was discovered in 1788, and prepared in small 

 quantities. It is now readily manufactured from the coal-tar product known as 

 carbolic acid, and is now an article of commerce as a cheap and brilliant yellow dye. 

 See PICRIC ACID. This, when mixed with saltpetre or chlorate of potash, particularly 

 with the latter, furnishes products which in violence of action more nearly resemble 

 gun-cotton and nitre-glycerine preparations than does any other readily explosive 

 agent. Both mixtures are susceptible of detonation by friction, and especially that 

 containing chlorate of potash, which is indeed inapplicable to practical purposes on 

 account of its dangerous nature. 



M. Designolle has produced safer mixtures of picrate of potash for artillery, small 

 arms, and for blasting purposes. One of these consisting of picrate of potash, salt- 

 petre, chlorate of potash, and charcoal gave satisfactory results. Mr. Abel informs us 

 that the picrate of ammonia incorporated with saltpetre furnishes one of the safest 

 explosive mixtures of a violent character yet produced. 



Colonia Powder is a modified gunpowder saturated with nitro-glycerine. 



Dualine is Schultze's sawdust powder impregnated with nitro-glycerine. 



Glyoxiline consists of a mixture of gun-cotton pulp and saltpetre converted into 

 porous pellets, which are saturated with nitro-glycerine, and afterwards coated with 

 varnish to protect it from damp. 



Lithofracteur. Lieutenant Trauzl, in his 'Explosive-Nitrilverbindungen,' describes 

 this preparation as simply a dynamite, in which an imperfect kind of gunpowder has 

 been substituted for a proportion of the siliceous earth ; and he gives the following as 

 the approximate percentage composition of the material : nitro-glycerine 52, siliceous 

 earth and sand 30, powdered coal 12, nitrate of soda 4, and sulphur 2. It has not 

 been found in practice equal to dynamite. 



Fulminates of Mercury and Silver. These violent explosive agents are used only 

 in the preparation of percussion caps, and have not been applied to any other useful 

 purpose. 



Iodide of Nitrogen and Chloride of Nitrogen will be described under their respective 

 heads. 



The following remarks on the ' Development of Force from Explosive Agents ' are 

 abstracted from Mr. Abel's paper read before the Institution of Civil Engineers in 1873. 



'The character of explosion and the mechanical force developed, within given 

 periods, by the metamorphoses of explosive mixtures, such as gunpowder, is subject 

 to modifications, and even the most violent explosive compounds known (the mercury 

 and silver fulminates, and the chloride and iodide of nitrogen) behave in different 

 ways under the operation of heat or other disturbing influences, according to the cir- 

 cumstances which attend the metamorphosis of the explosive agent (e.g. the position 

 of the source of heat with reference to the mass of the substance to be exploded, or to 

 the extent ^ of initial resistance opposed to the escape of the products of explosion). 

 Thus chloride of nitrogen, when covered with a film of water, explodes with great 

 violence when brought into contact with a decomposing agent ; but if the covering of 

 water is entirely removed, and the usual means are resorted to for causing the instan- 

 taneous decomposition of the liquid, its transformation into gases takes place with 

 little or no ^explosive violence. Again, if a heap of fulminate of mercury be ignited 

 at any portion of the exposed surface or immediately beneath it, the substance inflames 

 into a dull explosion, and but little mechanical work is performed ; but if the heap be 

 ignited in the centre, or near the base, the explosion is very violent, and considerable 

 shattering effect is produced. In these instances the covering of the water, on the one 

 hand, and the external portions of the heap of fulminate on the other, perform the 

 functions of the tamping in a blast-hole, or the walls of a shell, in determining accumu- 

 lation of pressure and consequent development of violent explosion at the point of 

 first ignition, which is then instantaneously transmitted through the mass. Applying 

 this result to practical purposes, it is found that by igniting a charge of powder at or 

 near the base in an ordinary blast-hole, considerable destructive force can be de- 

 veloped without the use of any tamping, as the upper portion of the charge acts itself 

 as tamping to the part first ignited, and develops its violent explosion. The destruc- 

 tive action is, of course, still further increased, if tamping be employed under the 

 above conditions. 



VOL. H. Y 



