454 



NATURE 



[December 24, 1914 



toluo], and ammonal. I'icric acid, with or without 

 the admixture of various ingredients, has been in 

 use at one time or another in most countries under 

 the names of melinite, lyddite, shimose powder, 

 etc. Lentil picric acid came into use, black gun- 

 powder formed practically the only explosive used 

 as a bursting- charge for shells, and the use of 

 picric acid was a great advance from the destruc- 

 tive point of view, as its explosive power was very 

 much greater. Picric acid, although sufficiently 

 insensitive to shock, has the property of readily 

 attacking metals and forming picrates, which are 

 much more sensitive and liable to explosion. This 

 involves special precautions in dealing with it, and 

 is an undoubted disadvantage. 



Ammonal is a mixture consisting of ammonium 

 nitrate, trinitrotoluol, charcoal, and aluminium 

 in fine powder. It is very safe, and is more power- 

 ful than picric acid, but owing to the hygroscopic 

 character of .ammonium nitrate, its chief constitu- 

 ent; it has specially to be protected from moisture, 

 which reduces and, if in sufficient quantity, de- 

 stroys its power of explosion. It is largely used 

 by the Austrians. 



Trinitrotoluol is undoubtedly now the most 

 widely used high explosive for military purposes 

 under the names of "Trotvl," " Tritolo," 

 "Tolite," "Tritol," "Trilite," and "T.N.T.," ac- 

 cording to the nation using it. 



"T.N.T.," as it is called in the British Service, 

 has attained its position by virture of its merits. 

 It is used in a state of great purity; it is chemi- 

 cally stable and without action on metals. It is 

 unaffected by water, and can be fused and run 

 into shells in the molten state. It is less sensitive 

 to shock than picric acid. Hard blocks of suit- 

 able size and shape are covered by electro-plating 

 them with a coating of copper, which prevents the 

 blocks from being broken and having their edges 

 chipped. In this form "T.N.T." is used for 

 demolishing bridges, etc. Although not quite so 

 powerful as picric acid, its other advantages make 

 it at present perhaps the best available explosive 

 for military use. 



The destructive effect of an explosion is caused 

 by the almost instantaneous conversion of the 

 solid explosive into gases, at a very high tempera- 

 ture, with consequent sudden exertion of an enor- 

 mous pressure. From the purely disruptive point 

 of view, the composition of the gas produced is 

 not necessarily of importance, the determining 

 factors being the volume of gas, the heat pro- 

 duced, and the velocity of detonation, ^^^hen how- 

 ever an explosion takes place in a confined space, 

 then in addition to the disruptive or shattering 

 damage, the components of the gas produced may 

 have an injurious effect on anyone having to 

 breathe it. 



In the case of explosives for use in civil life, 

 as in mining work, care is taken by adjusting the 

 composition of the explosive that the gases pro- 

 duced shall not have a deleterious effect on the 

 miner. In military operations this consideration 

 does not arise ; indeed, it may be maintained the 

 more deadly the effect of the fumes the better. 



Picric acid and "T.X.T." are definite chemical 



xo. 2 ^"^6. VOL. qa1 



bodies, but owing to insutticiency of oxygen are 

 not completely converted into gas on explosion, a 

 considerable amount of carbon being set free. 

 This accounts for the black smoke which is seen 

 when these bodies are exploded. 



In the earlier determinations, when explosives 

 which contained insufficient oxygen for complete 

 oxidation of the carbon and hydrogen w-ere fired 

 in a closed bomb, and the resulting gas analysed, 

 it was found that its composition was affected by 

 the density of loading. The higher the density 

 of loading the higher the pressure, accompanied 

 by increase of carbonic acid and decrease of car- 

 bonic oxide. Methane, which was absent or only 

 in very small quantities at low densities of load- 

 ing, increased steadily as the pressure increased. 

 It was, however, recognised that the composition 

 of the gas so found did not necessarily represent 

 the composition at the moment of explosion, for 

 the analysis was made some time after and when 

 the gas had cooled. Consequently reactions had 

 probably been taking place during the process of 

 cooling. Finally, it was thought that the forma- 

 tion of methane was not a real result of explosion, 

 but was due to secondary reactions during the 

 cooling stage. The experimental difficulties of 

 catching and fixing the gases at the moment of 

 explosion were overcome by detonating the explo- 

 sive in its own volume in a lead or porcelain bomb 

 placed inside a larger evacuated steel bomb. The 

 explosive had in this way to do work in bursting 

 the smaller bomb, and the rapidity of cooling of 

 the gas was thus so greatly increased that second- 

 ary reactions practically did not take place. When 

 fired under these conditions, which correspond 

 closely to those which exist when a shell explodes, 

 the gases from ammonal, picric acid, and 

 "T.N.T." were found to contain only small quan- 

 tities of methane. In addition to carbonic acid, 

 nitrogen, and hydrogen, ammonal contained about 

 24 per cent, and picric acid and "T.N.T." nearly 

 50 per cent, of the poisonous carbonic oxide. It 

 is thus evident that where shells burst in confined 

 spaces, in addition to the damage caused mechani- 

 cally, those persons breathing the fumes may be 

 fatally poisoned or seriously affected physiologi- 

 cally. 



It has been suggested that the ingredients of 

 shell charges may contain deadly poisons, but it 

 seems improbable that any poison intentionally 

 added to the contents of a shell would retain its 

 toxic properties after the shock and heat of ex- 

 plosion. As seen above, the gases from the 

 explosives now in use may be sufficiently poison- 

 ous under certain conditions. 



The subject of explosives seems often to create 

 a state of credulity, and to generate extravagance 

 of statement on the part of the non-expert writer 

 rarelv effected by other matters. The unknown 

 sometimes becomes truly appalling under his 

 imaginative pen. Even inventors have been 

 known to make wild statements in regard to their 

 explosives \ One should only accept with very 

 many grains of salt the sensational statements 

 which have appeared in some quarters as to the 

 weird and deadlv effects of recentlv-in vented ex- 



