i7« 



NA TURE 



[August 5, 1909 



tion, and at present preparations are being made for the 

 construction of a shed which will take in the largest 

 size of dirigible. The Admiralty has in prospect one great 

 rigid .dirigible, the War Olhce has three, and besides those 

 we have our balloons for war purposes. At the present 

 time we liave certain aeroplanes, and the prospect of two 

 new aeroplanes which are to be presented for experi- 

 mental purposes, and may hereafter be acquired. That 

 is the actual position of things. 



IMPROVEMENTS IN PRODUCTION AND 



APPLICATION OF GUNCOTTON AND 



NITROGLYCERINE.' 



II. 



T N the year 1846 Schonbein discovered guncotton. In the 

 ■'■ year 1886, that is, forty years later, the French chemist 

 Vieille invented his smokeless powder for military pur- 

 poses. This explosive, which was primarily designed for 

 use in the small calibre Lebel rifle, consisted essentially 

 of guncotton, and the secret of its success lay in the fact 

 that Vieille so altered its physical state that its rate of 

 combustion, when confined, was under complete control. 

 This condition was arrived at by treating the fibrous gun- 

 cotton with suitable solvents which entirely destroyed the 

 fibre and converted it into a colloidal, horny substance 

 quite devoid of all porosity. The gelatinised guncotton 

 resulting from this treatment burnt, when ignited, from 

 the surface inwards, and by varying the surface area any 

 required rate of combustion could be obtained. The use 

 of smokeless powders manufactured in this way was very 

 soon extended to all natures of ordnance. 



The next step in the development of smokeless powders 

 was the combination of nitroglycerine with nitrocellulose. 

 The first powder of this type was the " ballistite " of 

 Alfred Nobel, patented by him in the year 1S8S. The 

 original ballistite was composed of equal parts of nitro- 

 glycerine and of soluble nitrocellulose, a variety of gun- 

 cotton soluble in nitroglycerine, and no solvent was there- 

 fore required in its preparation, although a certain pro- 

 portion of camphor was used to promote the solution of 

 the nitrocellulose. Another form of nitroglycerine-nitro- 

 cellulose explosive is the British service powder, cordite, 

 which originally consisted of nitroglycerine, 58 parts, gun- 

 cotton, insoluble in nitroglycerine, 37 parts, and mineral 

 jelly, a product of the distillation of crude petroleum, 

 5 parts. To effect the gelatinisation of the guncotton, the 

 solvent acetone, obtained indirectly from the destructive 

 distillation of wood, is employed. The result of subject- 

 ing nitrocellulose in suitable machines to the action of 

 nitroglycerine or of solvents, of which there are several 

 suitable ones besides acetone, is to destroy its fibre and 

 convert it into a gelatinous mass, in which condition it 

 can be formed into any desired shape. Where solvents 

 are used to produce this result they remain in the mass 

 during subsequent operations, and are finally driven off 

 by means of heat. The resulting products, somewhat in- 

 correctly termed " powders," which are manufactured in 

 a variety of forms, such as grains and flakes of different 

 shapes, ribbons or strips, solid cords, tubes, &c., vary in 

 consistence with the quantity of nitroglycerine they con- 

 tain. The more nitroglycerine present the softer the 

 powder, pure nitrocellulose powders being hard to brittle- 

 ness. 



For practical purposes modern smokeless powders are 

 of two types : — 



(i) Those consisting entirciv of nitrocellulose, and 

 termed "nitrocellulose powders." 



(2) Those consisting of a mixture of nitrocellulose and 

 nitroglycerine, known as "nitroglycerine powders." 



Opinions differ somewhat as to the relative merits of 

 these two types ; in this country the latter tvpe is pre- 

 ferred. Their characteristic features are, briefly, as 

 follows : — 



A nitroglycerine powder is more powerful than a nitro- 

 cellulose powder, and the more nitroglycerine present the 

 more ^ powerful the explosive. Therefore, for equal 

 ballistics, a smaller charge of the former than of the latter 

 is required, and, consequently, the chamber capacity and 



1 Discourse delive'ed at the Royal In^tilution on Friday, January 20, by 

 Sir Frederic L. Nathan, R.A. Conlinued from p. 147. 



NO. 2075, VOL. 81] 



the size and weight of the breech mechanism are reduced ; 

 on the other hand, the higher the proportion of nitro- 

 glycerine the higher is the temperature of combustion and 

 the greater the erosive effects on the surface of the bore 

 of the gun. 



The presence of nitroglycerine in an explosive allows of 

 the more easy and rapid elimination of the solvent used 

 in manufacture and of moisture, a small quantity of which 

 is always present in nitroglycerine and guncotton. The 

 sooner this is attained the better, because the longer the 

 time that the powder is being heated in order to dry it, 

 the more likely is its chemical stability to be affected. 

 Moreover, it is a well-established fact that with nitrocellu- 

 lose powders it is iinpossible to remove the volatile matter 

 with anything like the same completeness as can be done 

 in the case of nitroglycerine powders. The consequence 

 is that the slow evaporation from nitrocellulose powders 

 of the residual volatile matter which takes place in store 

 tends to produce changes in their physical character and 

 renders them in course of time liable to alter in ballistic 

 properties, and even to develop dangerous pressures in 

 the gun. 



Nitroglycerine powders are cheaper than nitrocellulose 

 powders, weight for weight, and even more so for equal 

 ballistic effects. 



The original cordite, the manufacture of which com- 

 menced in 1890, contained a high proportion of nitro- 

 glycerine, 58 per cent., and the erosion produced, especially 

 in large guns, was considerable. This led to experiments 

 being carried out at W'altham .\bbey with the view of 

 the production of a less erosive explosive, and the final 

 result was the introduction into the service, in 1901, of 

 a modified cordite known as " cordite M.D.," in which 

 the percentage of nitroglycerine is reduced to 30 per cent., 

 so that the composition becomes : — nitroglycerine, 30 per 

 cent. ; guncotton, 65 per cent. ; and mineral jelly, 5 per 

 cent. 



The constants of explosion of cordite and cordite M.D., 

 determined at the Royal Gunpowder Factory some little 

 time ago, are as follows : — 



Explosive 



Cordite ... 

 CordileM.D. 



Density of 

 Loading 



0-2 

 02 



TT ...fc 1.. Total Gases. 



HeatofExpIo- ^^^^^ 



i^on at Constant, g^^^^,,^ 



volume. Water , = r- 



f^ at o L., 



Gaseous >„ „ ' 



700 mm. 



Temperature 

 of Explosi* 11 



Calories per 



gram c.c. per gram. *C. 



1156 87 1 I 2663 



965 920 2374 



An inspection of these figures shows that the alteration 

 in proportions of the explosive ingredients results in a 

 decrease in the heat of explosion of about 163 per cent., 

 and an increase in the volume of gases of about 55 per 

 cent., whilst there is a decrease of 289° C. in the tempera- 

 ture of explosion. 



As would therefore be expected, the erosion produced by 

 cordite M.D. is very much less than that produced by the 

 original cordite for the same ballistics, and is certainly 

 not greater, if as great, as that produced by the best 

 forms of nitrocellulose explosives. 



Although of minor importance to smokelessness, fiame- 

 lessness is a desirable quality for propulsive explosives to 

 possess. In this respect cordite M.D. is superior to cordite 

 in the case of rifles and machine guns ; unfortunately, a 

 suitable ingredient has not yet been discovered which will 

 render smokeless powders flameless in large guns. 



A third ingredient in both natures of cordite, viz. mineral 

 jelly, although present in a comparatively small propor- 

 tion, is a very important constituent. 



Cordite in the advanced experimental stage consisted of 

 nitroglycerine and guncotton alone, and as their combus- 

 tion produced no solid residue of any kind, the surface of 

 the bore of the magazine rifle in which the early experi- 

 ments took place was not fouled in any way. The result 

 was that the cupro-nickel coated bullets, propelled in 

 succession at high velocity through a clean barrel, de- 

 posited some of the cupro-nickel in the bore. In order 

 to prevent this a number of substances were incorporated 

 with the nitroglycerine and guncotton, with the object 



