Слике страница
PDF
ePub

useful form. They are made containing from 5 to 75 per cent. of nitro-glycerine. The lowest grades-5 to 10 per cent.-stand nearly on a level with ordinary blasting powder in regard to force and the purposes for which they are used. The powders ranging from 20 to 75 per cent. include most of the so-called high explosives now so largely manufactured in this and other countries. Those containing from 30 to 60 per cent. are the most extensively used. Serviceable powders must retain their nitro-glycerine at all practical temperatures, but must not be too dry, as they are then more difficult to handle.

In some powders the vehicle or solid matter with which the nitroglycerine is mixed is entirely inert (for example, the silicious earth from which Nobel's dynamite is made), while in others the absorbents are substances themselves capable of decomposition or action either directly or under the powerful influence exercised by the nitro-glycerine explosion, so that they affect the resultant force exerted. From this we have the classification adopted by some writers, of preparations having an inactive base and those having an active base; but this classification is not satisfactory, since it is the nitro-glycerine which is the essential and important constituent, and since the bases or vehicles used are not definite substances or mixtures; therefore, although the absorbent materials might be such as could form an active base, yet from the proportions or manner of admixture employed they may practically exert no influence. The character of the absorbent may exercise influence upon the explosion of the powder in several ways. It may be composed of bodies which will react and add to the gas generated and so to the force exerted. Its physical condition may be such as to contain the nitro-glycerine in a state favorable to its best use. Also upon it depends the density of the finished powder, a matter of considerable practical importance.

Of the powders with inert absorbent, Nobel's or Kieselguhr dynamite is a good example. Another is the Magnesia Powder, or Hercules No. 1, in which carbonate of magnesia is the absorbent. Still another is the Cellulose Dynamite of Trauzl, in which purified wood pulp is the vehicle. These are rich powders-70 to 80 per cent. of nitro-glycerine-and are but little used commercially. They are well adapted for military purposes and are so applied.

There are very many kinds or varieties of the lower grades of nitro-glycerine powders, but essentially they are much alike in general composition. As the quantity of nitro-glycerine to be taken up is

moderate, great absorptive capacity is not required. Usually the absorbent is a mixture composed of nitrate of soda with one or more combustible substances, such as sawdust, wood pulp, charcoal, coal, rosin, etc., etc. If in such a preparation the nitrate and the combustible are properly proportioned and thoroughly mixed, they take part in the reaction and add force to the result. But in many cases these materials are in such bad proportions, or so imperfectly mixed, that little or no valuable action can take place between them. In this connection it is not necessary to enter into detailed descriptions of particular powders to be found in the market. Those of this class are less valuable for military use than the richer ones, but of course can be made to serve quite well for torpedoes, etc., in case of need.

Explosive gelatine or gelatine dynamite is made by dissolving photographic gun-cotton in nitro-glycerine, or by mixing nitro-glycerine with collodion, removing the solvent by evaporation. Nitro-glycerine, with the aid of heat, dissolves soluble gun-cotton, forming a gelatinous mass of firmness varying with the amount of gun-cotton contained. At 160°-170° F. solution of the gun-cotton and gelatinization quickly take place. In explosive gelatine the nitro-glycerine is very strongly retained, not being given up under heat or pressure. Explosive gelatine is very insensitive to blows and is not easily exploded, requiring a very powerful fuse, and is not injured by water. Various substances may be mixed with the materials used in preparing this agent to form mixtures of different kinds. Camphor dissolves freely in nitro-glycerine, so that camphorated explosive gelatine can easily be made containing it in any desired proportion. This preparation is even more insensitive to blows or other mechanical action than the simple gelatine. When struck by a rifle bullet fired at a distance of So feet it does not explode. To determine its explosion, either strong confinement or a peculiarly powerful fuse is required. In many respects explosive gelatine (particularly the camphorated variety) has special advantages for military purposes. It is considerably stronger than dynamite (75 per cent.) or compressed guncotton, and it is very free from liability to accident or injury in use or transportation. On the other hand its stability is a matter of question. Instances of its decomposition on keeping or after long exposure to moderate temperatures have been observed. It is probable that this difficulty may be removed. Soluble gun-cotton is apt to contain traces of free acid and to vary greatly in composition. Special care must be taken in making the gun-cotton to insure uniformity and

complete purification. If this tendency is overcome it is probable that explosive gelatine may be valuable for military purposes.

Some of the instances of decomposition of explosive gelatine have been cited in these Proceedings, Vol. VII, p. 486. In a prefatory note to Addendum I. of Gen. Abbot's report upon Submarine Mines, he states that "all the samples of the explosive gelatine remaining on hand after the trials detailed in the report have undergone spontaneous decomposition, separating into cellulose and free nitroglycerine, with the copious evolution of nitrous fumes. This change occurred during the winter and spring of the current year (18811882), and was not caused by any exposure to high temperatures while in store."

A case of spontaneous decomposition of a small amount stored, freely exposed to air, in a dry room of even temperature, has occurred under my own observation. The camphorated explosive gelatine was wrapped in paraffine paper and then in light-brown wrapping paper. After something more than one year's exposure it was found in the early winter to be giving off nitrous fumes which had stained the wrapping paper, and to have shrunk considerably in volume, and that the outside of the paper was covered with congeries of fine crystals, while the odor of camphor was very strong. It was immediately put in a vessel of water, and after a short time the mass, which was friable, disintegrated. The camphor odor soon disappeared and the water became of a straw color, gave a strong acid reaction, and showed a slight trace of nitrous acid, but no nitric acid. On evaporation of the filtered liquid, oxalic acid crystallized out in quantity, and on evaporation of the mother liquid farther, on the water bath, a sugar-like mass was obtained which gave the glucose reaction with Fehling's solution.

The paraffine was regained unchanged and the paper was recovered, but in a flocculent condition, and with the color bleached from the brown. Careful search failed to reveal the presence of glycerine, nitro-glycerine or gun-cotton. The cellulose from the gun-cotton could not well be detected (if it existed) in the presence of so much flocculent cellulose from the paper.

The results obtained by De Luca in his "Researches on the Spontaneous Decomposition of Gun-Cotton," Comptes Rendus, 59, 487, September 12, 1847, are interesting in this connection. Gun

cotton decomposes most rapidly when heated to 50° on a water bath, next by sunlight, more slowly by diffused light, and very slowly in darkness. The gun-cotton first shrinks to % of its original volume, next it begins to become gum-like and sticky, then it swells; during all these phases it gives off nitrous fumes, but especially during the last. For the fourth phase the gas ceases to be evolved, and the mass becomes brittle and of a light color like sugar. The products are nitrous compounds with formic and acetic acids in the state of a gas, and an amorphous, porous, sugar-like body, almost entirely soluble in water and containing an abundance of glucose, gummy matter, oxalic acid, a small quantity of formic acid, and a new acid, of which he obtained the lead and silver salts for later examination. From 100 grams of gun-cotton he obtained about 14 grams of glucose.

As regards the decomposition of nitro-glycerine, A. Brull states, on page 26 of his "Études sur la Nitro-glycérine" (Paris, 1875), that concentrated sulphuric acid, cencentrated nitric acid and concentrated soda solution attack nitro-glycerine even in the cold and provoke a progressive decomposition. Nitro-glycerine, which retains a trace of free acid, is not stable. In general, the decomposition is extremely slow and tranquil. It disengages at first nitrous vapors, the liquid taking a greenish color. Then there is formed nitrogen and carbon dioxides and crystals of oxalic acid, and after some months the entire mass is transformed into a greenish, gelatinous matter composed of oxalic acid, water and ammonia. Sometimes, if the temperature is high, as when heated by the sun, the decomposition is more active, but it very rarely causes an explosion.

Major W. McClintock, R. A., has been making a series of experiments with small shot in order to test the accuracy of various statements as to the strength of Schultze powder (sawdust powder) and E. C. powder (granulated gun-cotton), and also to determine the velocity when black gunpowder was used, since little was known concerning this. The Boulengé chronograph was used for measuring the observed velocities and Bashforth's tables were employed for calculating the remainder. All the cartridges used were bought from the same tradesmen, who obtained them direct from the factory, and although the method of loading was identical in all, and the powder (in those charged with gunpowder) was supposed not to vary in quality, it was found that no two boxes gave similar results. The cartridges were then examined, and it was almost invariably found that

the amount of powder was deficient and the weight of shot in excess. This deficiency of powder amounted in one case to 8 grains, and the excess of shot in the same cartridge to 64 grains. The powder too was found to vary in appearance and size of grain, and when some cartridges from each box were stripped and carefully reloaded with correctly weighed charges, the muzzle velocities showed that the powder varied very much in strength. These experiments show that the mean velocity obtained with unweighed charges should not be considered as proof of the quality of the cartridges, because one or two rounds which have a heavy powder, or light shot charge, may unduly raise the average. Taking weighed charges of 492 grains (1 oz.) of shot, 82 grains (=3 drams) of gunpowder, and from 45 to 47 grains of Schultze or E. C. powder, it was found that the average velocity of the last two was over 100 f. s. greater than gunpowder. The determined velocities of even the carefully made-up charges showed considerable variations, but source of error exists in the use of small shot, owing to the fact that the quickest pellets of the charge need not always cut the wires but may pass through the meshes. Major McClintock thinks that his experiments with the Schultze and E. C. powders were so few that it would be premature to form any decided opinions concerning them at present, but he states that these explosives possess great strength (sometimes too great), make little smoke and cause slight fouling, but the velocities they give are not regular. These experiments are given very much in detail, with copious tables, and are accompanied by an account of researches made to determine how the boring of the gun-barrels affects the muzzle velocity.—(Proc. Roy. Artil. Inst. 12, 332, Aug. 1883.)

In these notes, Vol. VIII, p. 444, an abstract of the testimony in the case of the Atlantic Giant Powder Co. against the Dittmar Co. is given. Recently some of the papers in the suits of the same company against George A. Goodyear, George W. Townsend, Michael Brady, and the Neptune Powder Co. have come into our hands. The compositions of the various explosives which the Atlantic Giant Powder Co. regarded as infringements of their patents were as follows:

[merged small][ocr errors][merged small][merged small][merged small][merged small]
« ПретходнаНастави »