524 



NATURE 



[June 23, 1921 



Some War Developments of Explosives.^ 



By Sir Robert Robertson, K.B.E., F.R.S. 



IT is not proposed to describe the great 

 factories that arose during the war for 

 the manufacture of explosives, but to indicate 

 by one or two examples some of the conditions 

 which led to developments. 



Production. 



The enormous weekly production was reached 

 of 1500 tons of trinitrotoluene, 300 tons of picric 

 acid, 3000 tons of ammonium nitrate, and 2000 

 tons of cordite. To produce these were required 

 such weekly quantities as the following : 6600 

 tons of pyrites, or 2700 tons of sulphur, 8300 tons 

 of Chile saltpetre, 720 tons of toluene (from 

 600,000 tons of coal), 162 tons of phenol (which 

 would have required 1,000,000 tons of coal, if syn- 

 thetic production had not been established), 700 

 tons of ammonia (from 250,000 tons of coal), 374 

 tons of glycerine (from 2700 tons of fat), 700 tons 

 of cotton cellulose (from 1060 tons of wastes), and 

 1200 tons of alcohol and ether (from 4200 tons of 

 grain). 



These numbers indicate not only the magnitude 

 of the production, but also the interdependence of 

 a large number of industrial chemical activities, 

 and, although many of the products were derived 

 from our own coal, it brings home the dependence 

 of the country on overseas transport of many of 

 the essential substances, such as pyrites, sulphur, 

 Chile nitrate, and cotton. 



Firing and Detonation of a Shell. 



The Propellant. — -The processes for the manu- 

 facture of cordite and of its ingredients had been 

 the subject of study, and considerable advances 

 had been made, so that it might fairly be claimed 

 that this country led the way in the technique and 

 safety precautions involved in the manufacture of 

 propellants'. The existing factories were also cap- 

 able of extension, until the demand became so 

 great that additional ones had to be erected. 



At first, the propellant used was cordite M.D., 

 composed of nitroglycerine, guncotton, and 

 mineral jelly, in which acetone was used to gela- 

 tinise the guncotton. A nitrocellulose powder 

 obtained from America was also used. The 

 demand for propellant to be made in this country 

 ultimately reached 1500 tons a week, and this, 

 even with an efficient system of acetone recovery, 

 would have involved an expenditure of that sol- 

 vent of above 400 tons a week. On account of the 

 shortage of supply of this solvent, a new propel- 

 lant for the Land Service was introduced — cordite 

 R.D.B. — in which ether-alcohol was substituted 

 for acetone as a solvent, a change necessitating 

 the choice of a nitrocellulose of a lower degree 

 of nitration than guncotton, and alterations in the 

 proportions of the other ingredients. For the 



_^ Summary of a Friday evening discourse delivered at the Royal Institu- 

 tion on May 6. 



NO. 2695, VOL. 107] 



new propellant the conditions were laid down and 

 met that it should have the same heat energy, 

 that it should give the same ballistics as cordite 

 M.D., in order to avoid alteration in calculating 

 ranges from data obtained with the older pro- 

 pellant, and that it should be capable of being 

 manufactured by the machinery available and with 

 the technique of manufacture known in the 

 country. 



The main changes introduced were in the manu- 

 facture of the nitrocellulose and in the supply of 

 the solvent. As ether-alcohol is a less powerful 

 solvent than acetone, even for the special nitro- 

 cellulose employed, a strict definition of the nitro- 

 cellulose was necessary, and the necessity to pro- 

 vide this in suitable form led to much investiga- 

 tive work on the nature of the cellulose, with the 

 result that its manufacture was brought under a 

 system of strict chemical control. This control had 

 among its objects the elimination of ligneous im- 

 purities and the standardisation of the viscosity 

 of the cellulose, since if its viscosity were uniform 

 and low, it was found that the gelatinisation of 

 the nitrocellulose when incorporated with the 

 nitroglycerine and mineral jelly was greatly facili- 

 tated, and the production of uniform cords 

 assisted. Ligneous matter in the cellulose was 

 rendered visible by a process in which the woody 

 matter was selectively dyed, and the viscosity 

 of the cellulose was measured by the rate of fall 

 of a steel sphere falling through a solution of 

 cellulose. 



The supply of alcohol was obtained entirely 

 from the distilleries of this country, and a lar^e 

 plant for converting a portion of it into ether was 

 erected at Gretna. Nearly looo tons of alcohol, 

 or the equivalent of about 200,000 gallons of 

 proof spirit, were required for the production of 

 the 1500 tons of R.D.B. cordite a week, and this 

 requirement it was which led to the restricted 

 sale and increased cost of whisky. 



The High Explosive Shell. 



Prior to the war the Land Service used for 

 the most part shrapnel shell, designed to project a 

 shower of lead bullets, efficacious against per- 

 sonnel, but of little value in attacking fortified 

 positions, for which high explosive shell are 

 required. 



Shrapnel was very largely used by the Land 

 Service throughout the war, but the earlier 

 type of high explosive shell filled with lyddite 

 (picric acid), and brought to explosion by the ig- 

 nition of a fiercely burning mixture, was aban- 

 doned for one in which true detonation was 

 secured with certainty. The latest type of high 

 explosive shell was exemplified by a 4-5-in- 

 howitzer shell fitted with a graze fuze (Fig. i). 



The Fuze.— A graze fuze is a mechanism which 

 gives rise to a flash when the shell grazes on 



