No. VI.
*As it is proposed to continue these Notes from time to time, authors, publishers and manufacturers will do the writer a favor by sending him copies of their papers, publications or trade circulars.
In No. V of these Notes we have referred to Berthelot's lectures on Explosives. These have now been reprinted by Van Nostrand as No. 70 of his Science Series, We then proposed to present later his discussion of the theories suggested to account for explosions induced by the influence of contiguous explosions, and hence we extract the following.
In discussing the duration and speed of propagation of explosive reactions Berthelot has regarded the development of the explosive reactions either from the point of view of their duration in a homogeneous system in which all the parts are maintained at the same temperature, or else from the standpoint of their propagation in a system equally homogeneous, to which fire is applied directly by means of a body in ignition, or else by a violent shock. In these later years, however, the study of explosive substances has revealed the existence of another method of propagating the reactions from an explosive centre, this propagation taking place at a distance and by the intermediation of the air or certain solid bodies which do not themselves participate in the chemical change.
We shall now speak of what are called explosions by influence, whose existence was formerly suspected from certain known facts connected with the simultaneous explosion of several buildings separated by considerable space from each other, as in catastrophes occurring in powder mills. Attention has been especially directed to this class of phenomena by the study of nitro-glycerine and guncotton.
We will begin by giving the most important characteristic facts. A dynamite cartridge made to detonate by means of a fulminate cap causes the adjoining cartridges to detonate, not only by contact and by direct shock, but even from a distance. In this way an indefinite number of cartridges, arranged in a regular course, may be made to detonate.
The distances to which the explosion may be propagated are relatively great. Thus, for instance, with cartridges contained in rigid metallic envelopes and placed on a resisting soil, the detonation produced by IOC grams of Vonges dynamite (75 per cent, of nitroglycerine and 25 per cent, randanite, which is very finely divided silica) communicates itself 0.3 meter, according to the experiments of Captain Coville. D being equal to the distance in meters and C the weight of the charge in kilograms, the experiments of this officer show that D =z 3.0 C. When the caps were laid on a rail D was found to be equal to 7.0C On soft or ploughed-up earth the distances, on the contrary, are less. When a cartridge is suspended in air there is no detonation by influence, perhaps because the cartridge not being fixed can recoil freely, which diminishes the violence of the shock. Nevertheless there are experiments which show that the air suffices for the transmission of the detonation by influence, although with greater difficulty and requiring a greater mass of the explosive. With a dynamite less rich in nitro-glycerine (55 per cent, of nitro-glycerine and 45 per cent, of" the argillaceous ashes of boghead coal), contained in similar cartridges, and placed along the ground, the experiments of Captain Pamard have given the smallest distances: Dzizo.goC. If metallic envelopes having less resistance are used, the distance at which the explosion is propagated is likewise diminished. Dynamite simply spread along the ground ceases to propagate the explosion. The experiments performed in Austria have given similar results. They have shown that the explosion is communicated either in the free air with intervals of 4 cm., or else through pine boards 18 mm. thick. In a lead tube with a diameter =0.15 meter and a meter in length, a cartridge placed at one extremity has caused the detonation of a cartridge at the other end. The explosion is still better transmitted through tubes made with wrought iron. The couplings of the tube diminish its aptitude for transmission.
An explosion which is propagated in this manner will go on weakening itself from cartridge to cartridge and even change its character. Thus according to the experiments made by Captain Miintz at Versailles, in 1872, a first charge of dynamite exploded directly, excavated a funnel-shaped hole in the ground with a radius of 0.30 meter; the second charge, detonated by influence, produced an opening of only 0.22 meter; the effect of the detonation was then reduced. This reduction should manifest itself towards the limit of the distance at which the influence ceases. In the same way four tin screens were located 40 mm. apart, a small cylinder of gun-cotton was placed against each of them, and the entire affair arranged on aboard; 15 mm. in front of the first screen a similar cylinder was detonated. All of the cylinders detonated, but a progressive diminution was observed in the indentations produced in the board below each cylinder. According to these facts the propagation by influence depends at the same time on the pressure acquired by the gas and on the nature of the support. It is not even necessary that it should be rigid.
Finally, in operating under water at a depth of 1.30 meters, a charge of 5 kilograms of dynamite brought on an explosion of a charge of 4 kilograms situated at a distance of 3 meters. The water then transmits the explosive shock, at least to a certain distance, as does a solid body. This transmission is so violent that the fish are killed in ponds within a sphere of a certain radius by the explosion
of a dynamite cartridge.
Similar experiments have been made by Abel with compressed gun-cotton. According to his observations the explosion of the first block determines that of a series of similar blocks. The propagation under water has likewise been studied ; the explosion of a torpedo charged with fulminating cotton caused the detonation of adjoining torpedoes placed within a certain radius of activity. The sudden pressure transmitted by the water when measured by means of the compression of lead at different distances, such as 2.50 m., 3.50 m., 4.50 m., 5.50 m., goes on decreasing, as would be expected. Besides, experiment has shown that the relative position of the charge and of the " crusher " is of no consequence, which is in harmony with the principle of equal transmission in all directions of hydraulic pressures.
Explosions of fulminating substances which are rapidly propagated to a great number of caps, belong to this same order of explosions by influence.
We have previously cited the explosion in the Rue Beranger. The experiments which M. Sarrau made on that occasion showed that caps of the description which produced this catastrophe may be successively burned in a fire without giving rise to a general explosion; whereas the explosion of a few of these same caps, each containing lo milligrams of explosive material, if it is provoked by a rapid pressure, determines by influence the explosion of the adjoining packages, even when they are not contiguous and are situated at a distance of 15 centimeters apart. A general explosion may thus easily be produced by influence. It follows then from these facts, and especially from the experiments made under water, that the explosions by influence are not due to inflammation, properly so called, but to the transmission of a shock arising from the enormous and sudden pressures produced by the nitro-glycerine or the gun-cotton.
Let us enlarge upon this explanation; it is the same fundamentally as that which we have already shown as accounting for the influence of the shock which determines the direct detonation of explosive substances.
In an extremely rapid reaction, the pressures may approach to the limit which corresponds to the matter detonating in its own volume, and the commotion due to the sudden development of almost theoretical pressures can be propagated both through the ground and supports as intermediary, or through the air itself, projected en masse, as has been shown by the explosion of certain powder factories and of gun-cotton magazines, and even by some of the experiments with dynamite and compressed gun-cotton. The intensity of the shock propagated either by a column of air or by a liquid or solid mass varies with the nature of the explosive body and its mode of inflammation; it is of greater violence according as the length of the chemical reaction is shorter and develops more gas, that is to say, a higher initial pressure, and more heat, and consequently work, for the same weight of explosive material.
This transmission of a shock is conveyed better by solids than by liquids, better by liquids than by gases; with gases it becomes better as they are more compressed. Through solids it is better propagated according to their degree of hardness, iron transmitting it better than earth, and hard ground better than ploughed soil. All breaks of continuity in the transmitting material tend to weaken it, especially if a softer substance is interposed. Thus it is that the use of a tube made from a goose-quill, as a receiver, stops the effect of mercury fulminate, while a tube or a capsule of copper transmits this effect in all its intensity. The explosion by influence is the better propagated in a series of cartridges according as the envelope of the first detonating cartridge is the more resisting, which allows the gases to attain a greater pressure before the covering is destroyed. The existence of an empty space, that is to say, filled only with air, between the fulminate and the dynamite, on the other hand diminishes the violence of the shock transmitted, and in consequence that of the explosion; generally the effects of breaking powders are lessened when there is no contact. To form a full conception of the transmission of sudden pressures which produce shock by the supporting medium, it is desirable to recall this general principle, in virtue of which, in a homogeneous mass, pressures are transmitted equally in all directions, and are the same on a small element of surface whatever its position. Detonations produced under water with gun-cotton show that this principle is equally applicable to the sudden pressures which produce the explosive phenomena. But it ceases to be true when one passes from one medium to another.
If the inert chemical matter which transmits the explosive movement is fixed in a given situation on the surface of the ground, or better, on the surface of the rail on which the first cartridge was placed, or better still, held by the pressure of a mass of deep water in the midst of which the first detonation is produced, the propagation of the movement in this matter will hardly be able to take place, except under the form of a wave of a purely physical order, and consequently of an essentially different character from the first wave of a chemical and physical order simultaneously developed in the explosive body itself This new wave propagates the concussion away from the explosive centre all around it, and with an intensity which decreases inversely as the square of the distance. Even in the neighborhood of the centre, the displacements of the molecules may break the cohesion of the mass and disperse it, or crush it by enlarging the chamber of explosion, if the operation is conducted in a cavity. But at a very short distance (the magnitude of which depends on the elasticity of the surrounding medium) these movements, confused at the beginning, arrange themselves in such order as to produce a wave, properly so called, characterized by compressions and sudden deformations of the material, the amplitude of these oscillations depending upon the magnitude of the initial impulse. They move with a very great rapidity, and preserve their regularity up to the point where the medium is broken; then these compressions and sudden deformations change their nature and are transformed into a movement of impulse, that is to say, they reproduce the shock. If then they act on a new cartridge they may determine its explosion ; the shock will be otherwise weakened by the distance, and in consequence the character of the explosion may be modified. The effects diminish in this manner up to a certain point from which the explosion ceases to produce itself When this occurs on a second cartridge the same series of effects will be produced from the second to the third cartridge; but they depend on the character of the explosion of the second cartridge. And thus it goes on.
Such is the theory that appears to me to explain explosions by influence and the phenomena which accompany them. It depends, definitely, on the production of two orders of waves: one series represents the explosive waves, properly so called, developed in the midst of the matter which detonates, and consists of a continually reproduced transformation of the chemical actions into thermal and mechanical actions, which transmit the shock to the support and to the contiguous bodies; the other is a purely mechanical and physical series, which transmits equally the sudden pressure all around the centre of the concussion to the adjoining bodies, and by a singular circumstance to a new mass of explosive material.
A theory differing from this was originally proposed by Abel. It is the theory of Synchronozis vibrations. According to this English savant the originating cause of the detonation of an explosive lies in this synchronism between the vibrations produced by the body which provokes the detonation and those which the first body would produce in detonating, precisely as a violin string resounds at a distance in unison with another vibrating chord. Prof. Abel has recited the following facts in support of his theory. To begin with, the detonators appear to differ with each variety of explosive. For instance, nitrogen iodide cannot cause the detonation of compressed gun-cotton. Nitrogen chloride will not produce the same detonation except when ten times as much weight is used as of the fulminate necessary. Likewise nitro-glycerine will not produce a detonation in sheets of gun-cotton on which is placed a case containing nitro- glycerine. In this way nitro-glycerine up to 23.3 grams can be detonated without effect. On the other hand, 7.75 grams of compressed gun-cotton have caused the detonation, at a distance of 25 mm., of nitro-glycerine wrapped up in an envelope of thin sheet-iron. Likewise, according to Brown, a cap filled with a mixture of potassium ferrocyanide and potassium chlorate will not detonate gun-cotton. Finally, according to Trauzl, a cap consisting of a mixture of mercury fulminate and potassium chlorate should be of much heavier weight than if it be filled with the pure fulminate ; nevertheless, the heat given off by the same weight is greater by one-fifth with the first mixture.
Messrs. Champion and Pellet have brought to the support of this ingenious hypothesis the following experiments : They attached to the strings of a double bass particles of nitrogen iodide, a substance which detonates on the slightest friction. Then they made the strings of a similar instrument vibrate at a short distance off; a detonation was produced, but only for sounds higher than a certain note which
corresponds to 60 vibrations per second. They also took two conjugate parabolic mirrors, placed 2.5 meters apart, and they arranged along the line of the foci at different points several drops of nitroglycerine or of nitrogen iodide ; they then detonated at one of the foci a large drop of nitro-glycerine; they observed that the explosive substances placed in the conjugated foci detonated in unison, to the exclusion of the same substances placed at the other points. A layer of lamp-black placed on the surface of the mirrors was designed to prevent the reflection and the concentration of the heat-rays.
As yet none of the experiments appear to me to be conclusive, and several of them seem even to be directly opposed to the theory. We shall begin by observing that the characteristic feature of a given musical note, capable of determining each variety of explosion, has never been established. It is only below a certain note that the effects cease to be produced, while they take place by preference, whatever the explosive bodies may be, by the action of the most acute notes. Besides, these effects cease to produce themselves at distances which are incomparably less than the resonance of the chords in unison, which goes to prove that the detonations are functions of the intensity of the mechanical action, rather than of the character of the determining vibration. Similarly, the detonation ceases to be produced when the weight of the detonator is too slight, and in consequence when the mechanical energy of the shock is weakened. Nevertheless, the specific vibratory note which determines the explosions should always remain the same. For instance, cartridges filled with 75 percent, of dynamite cease to detonate when the capsule contains a weight of fulminate less than 0.2 gram, the detonation only being assured in all cases by the regulation weight of one gram. This confirms the existence of a direct relation between the character of the detonation and the intensity of the shock produced by one and the same detonator.
If it is true that gun-cotton will cause the nitro-glycerine to detonate in consequence of the synchronism of the vibration communicated, then we do not understand why the reciprocal action does not take place; while the absence of reciprocity can be easily explained by the difference of the structure of the two substances which plays so important a part in the transformation of the mechanical energy into work.
This same diversity of structure and the modifications which it introduces into the transmission of the phenomena of the shock and the transformation of the mechanical energy into thermal energy, may be cited to explain the facts observed by Abel.
The difference between the energy of pure fulminate and of the fulminate mixed with potassium chlorate is no less easily explained; the shock produced by the first body being sharper on account of the absence of all dissociation of the product (which is no other than carbon monoxide), this absence should be contrasted with the dissociation of carbon dioxide formed in the second case. Perhaps, also, the formation of potassium chloride disseminated through the gas produced, with the concurrence of potassium chlorate, weakens the shock, just the same as silicon does in the case of dynamite.
All the effects observed with nitrogen iodide may be explained by the vibration of the supports and by the effects of rubbing which result there from, this substance being particularly sensitive to friction. The experiment with the conjugate mirrors may also be easily explained by the concentration in the focus of the movements of the air, and therefore of the mechanical effects which result.
Besides, M. Lambert has proved by experiments made for the Commission on Explosive Substances, that in the explosion of dynamite cartridges in tubes of cast iron of large diameter, regarded from the standpoint of detonations by influence, there does not appear to be any difference between the ventral segments and the nodes characteristic of the tube.
Desiring to clear up this entire question by removing it from the influence of the support and of the diversity of cohesion and physical structure of solid explosive substances, I undertook a series of special experiments on the chemical stability of matter in sonorous vibration, and especially on that of gaseous bodies such as ozone, hydrogen arsenide, or liquids such as hydrogen peroxide and persulphuric acid, all of these bodies being selected from among those which decompose or change spontaneously at ordinary temperatures with the disengagement of heat, precisely as explosive substances do. The description of these experiments may be found in the Comptes Rendus
or in the Revtie Scientifique, May, 1880.
They lead to the conclusion that substances, which are transformable with the disengagement of heat, are stable under the influence of sound waves, while they are decomposed under the influence of ethereal vibrations. This diversity in the mode of action of the two classes of vibrations is not surprising when we consider that the most acute sonorous vibrations are incomparably slower than the luminous or thermal vibrations.
Hence it appears certain that the propagation of explosions by influence is not made in virtue of an undulatory movement, which is a complex motion of a chemical and physical order in the midst of the explosive substance which is decomposed, while it is purely physical in the midst of intermediary substances which suffer no decomposition ; but that which distinguishes this sort of movement of the vibrations, properly so called, is, first of all, its extreme intensity, that is to say, the magnitude of the mechanical energy which it transmits ; it is also the unique character of the explosive wave, which is propagated in contradistinction with the multiplicity of successive sonorous waves. Finally, it is essential to observe that the explosive material does not detonate because it transmits the movement, but on the contrary because it arrests it, and because it transforms on the spot the mechanical energy into thermal energy, capable of suddenly raising the temperature of the substance up to the degree which will produce its decomposition.
On page 670, Vol. VIII, we have referred to a new explosive called Panclastite, invented by Eugene Turpin. We are now in possession of a brochure by the inventor, and from this we learn that the substance is made by mixing liquid nitrogen tetroxide (N2O4) with combustible substances such as the hydrocarbons ; vegetable, annual and mineral oils ; fats and their derivatives, but preferably with carbon disulphide. He proposes that the two substances should be kept apart until needed for use, when they may be mixed in the proportions considered best for the work in hand. The proportions which yield the most sensitive mixture are 2CS.' -|- 3N2O4, being about two volumes of the first to three volumes of the second. In making this mixture the temperature falls about 20°. When equilibrium is re-established the mixture burns with a most brilliant flame if ignited when freely exposed to the air. If confined in a vessel and ignited it burns until the pressure of the gases produces an explosion. Under these circumstances only a portion of the enclosed matter explodes and the remainder burns up quietly. If however it be exploded by a fulminate primer, whether confined or freely exposed, the explosion is complete and powerful; more powerful, it is claimed, than nitroglycerine or explosive gelatine. The reactions attending these different modes of decomposition vary. When the panclastite burns freely it leaves a deposit of sulphur, and sometimes of colorless crystals which yield nitrogen dioxide when brought in contact with water. When the panclastite is detonated carbon is deposited as a black residue.
The deposition of sulphur can only be explained by supposing a deficiency of nitrogen tetroxide. The formation of nitrogen dioxide or monoxide cannot be admitted, since carbon disulphide burns equally well with these two gases.
The advantages claimed for this explosive are greater power than dynamite, perfect safety of the separate constituents in transport and storage, insensitiveness of the mixture to blows, and easy control of the manufacture by the government, owing to the fact that nitrogen tetroxide is not met with in commerce.
The power is shown in the results of several experiments cited, where rocks and rails were broken and cylinders of lead compressed. Thus where 400 grams of dynamite No. I broke blocks of stone into 5 or 6 portions, 150 grams of panclastite broke them into 28 to 32 portions.
At 100° the gas consists chiefly of NO2, at ordinary temperatures of N'-Oj, and at intermediate temperatures the gas is a varying mixture of these two. The liquid, at ordinary temperatures, gives off an abundance of reddish vapors, which, when mixed with air, are extremely difficult to condense. These vapors have a pungent, suffocating odor, an acid taste, are quite irrespirable, and stain the skin of a bright yellow. When mixed with water at a low temperature it is decomposed into nitric and nitrous acids ; at an ordinary temperature, into nitric acid, water, and nitrogen dioxide.
The Notes on Explosives of W. N. Hill have been regarded as a most valuable and trustworthy guide to this study. The recent limited edition having been exhausted, we extract the following new notes, which correct, explain or extend the statements and descriptions of former editions.
The features of the nitro-glycerine process which are of the greatest importance are the strength of the acids and the complete washing of the products. The nitric acid should be of the greatest strength, since upon this depends the completeness of the conversion. With such acid, the maximum production of nitro-glycerine is attained and the oxidizing action is lessened. Also in such case the heat of the operation is much reduced, and the temperature of the reaction becomes of less importance. With the strongest acid the limits of temperature heretofore assigned may be considerably exceeded without injurious result. It has been stated that the mixing of the glycerme with the acid should be slowly performed. This should be understood to mean that the mixing is to be slowly performed, in order to preserve a low temperature during the operation ; but, if the temperature is within the limit, the mixing should be performed as rapidly as possible, and the nitro-glycerine removed from the sphere of action. Rapidity of working is largely dependent upon the quality of acids employed, since the heat evolved is least when the strongest acid is used. In general with highly concentrated acid, not only is the proportional product increased, but also the reaction goes on more uniformly and is more easily controlled.
The manufacture of nitric acid for this purpose cannot be considered here, but it should be stated that acid for making nitro-glycerine is now largely sold in the form of " mixed acid "—that is, the mixture of nitric acid and sulphuric acid ready for use. Much of this, however, does not come up to the standard which should be set up. The degree of strength of the nitric acid given before is too low. Acid of 1.49 to 1.51 specific gravity (48°-49° B.) should be taken, and this strength should be real and not factitious, as is often the case with acids nominally testing 50° and 52° Baume. To prepare such acid requires special care and precaution. The method of redistillation from oil of vitriol in glass retorts furnishes the finest acid, and in the writer's hand has worked extremely well, but it involves some trouble and expense.
The proportion of nitro-glycerine obtained is dependent almost entirely upon the acid used. If the glycerine is weak the product will fall off, but the small difference in strength of glycerine ordinarily found exercises little effect. But if the acids are weak the product is markedly less. This does not depend to any extent upon the method or form of apparatus operated, but only upon the acid taken. Weak acids will carry smaller quantities of glycerine and give lower proportional products than strong ones. Consequently, statements of relative products obtained are of comparatively little value unless accompanied by a statement of the kind of acid employed and the relative amount of glycerine treated. We have stated that in operating practically 1.6 to 1.75 parts of nitro-glycerine to one of glycerine were obtained, but that with the strongest nitric acid 1.96 to 2.03 parts were produced on a small scale. These figures are too low. It is not difficult to practically carry the proportion to rather more than two to one, using one part of glycerine to 7.5 or 8 parts of acid (mixed). With some care in the preparation of materials 2.2 parts can be obtained.
The method of making nitro-glycerine fully described in the body of this work is a convenient one from simplicity of apparatus, and has been found serviceable for the occasional requirements of the torpedo station. But for steady work on a large scale it is not as desirable as other methods of operating. The handling of small quantities of material takes much time and labor, and the reaction goes on more steadily and regularly with larger masses of material. The simplest, and a very effective method, is to use a large amount of the mixed acid (2000 to 3000 lbs.) in a large leaden or iron tub, containing also coils of pipe through which cold water is forced ; this tub is set within another of wood, and the annular space between is traversed by cold water ; agitation of the acid is brought about by agitators driven by power (in some cases the agitators are driven by hand, but this is very objectionable). The glycerine is run in through an opening in the cover of the tub and distributed so as to fall upon the acid in a number of fine streams. The temperature is observed by a thermometer passing through the cover. When the desired amount of glycerine has been run in, the contents of the tub are drawn off into water and the nitro-glycerine separated.
In another form of apparatus a leaden tank is placed within a wooden one, so that water can be passed between them ; in the tank revolves a hollow shaft, carrying paddles for a portion of its length, and for the remainder a cylinder, so that cold water maybe led through the shaft and cylinder. The glycerine falls upon the surface of the revolving cylinder and is so conveyed into the acid, which is agitated by the paddles.
Different in principle is the process of Boutmy and Faucher. In this the glycerine is mixed with half the sulphuric acid and the mixture allowed to cool. This is then added to the mixed acid (the nitric acid with the remainder of the sulphuric), the whole allowed to stand for twenty-four hours, and then thrown into water to separate the nitro-glycerine. Special advantages are claimed for the method, but it is doubtful if these claims are well founded. It is stated that it is more free from danger than others, and that it gives a large yield. With proper care the operation of conversion is not a dangerous one, and accidents at that stage are extremely rare by any method. The yield claimed is not in advance of that usually obtained, and, as already pointed out, the yield is governed by the quality of the acid used. This method is open to the grave objection that a large proportion of the nitro-glycerine is in contact with strong acid for a considerable time.
In Kurtz's method the vessel containing the acid is a narrow cylinder, with conical bottom of lead or iron, placed vertically. Two pipes extend to the bottom of this cylinder, one delivering glycerine and the other compressed air. The openings of these pipes are opposite to one another, so that the air-current strikes the glycerine and quickly diffuses it through the acid. The nitro-glycerine formed is supposed to rise to the surface of the liquid, and run off through a pipe to the washer. In another form of Kurtz's apparatus air is forced into the glycerine, making a kind of emulsion, which is driven into
the acid in the converting vessel by air pressure.
In all forms of apparatus for making nitro-glycerine the greatest care must be taken to prevent any accidental admixture of water with the charge in the converter. A very little water shows itself by the greater trouble and slowness experienced in running, and the product falls off. But if more water enters, the heat developed would be greater than can be carried away by the usual means of cooling and the charge is "fired." Usually this means only an active decomposition, accompanied by clouds of nitrous vapors. Slight "fires" may be stopped by vigorous agitation, but if the firing is persistent the contents of the tub should be run off as rapidly as possible. During drawing off, constant agitation of the liquid should be made to prevent separation of nitro-glycerine. Washing with water is the only mode spoken of. It is not difficult to wash nitro-glycerine thoroughly with water only, but the treatment must be continued until the washing is complete. This requires considerable time and labor. It is usual in manufacturing, therefore, to use an alkaline solution (sodium carbonate) to assist and expedite the washing process.
Hill has heretofore stated that frozen nitro-glycerine could not be fired. This is an error, it can be fired, but with much greater difficulty than when in the liquid state. In many later experiments he has often both failed and succeeded in exploding the frozen material, with the usual and larger amounts of fulminate.
Nitro-glycerine is but little used in the liquid state. In this country the principal use made of it in this condition is for "torpedoing" oil-wells. But for most purposes, such as mining, quarrying, engineering work, etc., the liquid is very rarely taken, while powders of which it is an essential ingredient are very largely employed. There are very few instances in which the intense and local action of liquid nitro-glycerine is demanded, but the field for the application of nitroglycerine powders, which are more powerful and violent than ordinary blasting powder, is very extensive. These powders are of many kinds and many names. They may be considered in two ways:
1st. As nitro-glycerine preparations whose power and usefulness depend essentially upon the proportion of that substance which they contain ; and 2d, according to the absorbent with which the nitroglycerine is mixed. The nitro-glycerine is the valuable ingredient of all these powders. The principal object of their manufacture is to present nitro-glycerine in a safer, more manageable and more 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 percent, 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 80 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 (1881-1882), 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 gelatin was wrapped in parafifine 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 sunhght, more slowly by diffused light, and very slowly in darkness. The gun-cotton first shrinks to 1/10 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 "Etudes sur la Nitro-glyc6rine " (Paris, 1875), that concentrated sulphuric acid, concentrated 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 Boulenge 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 (==ii 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.
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 :
Vulcan Powder.
Nitro-glycerine 32.60 per cent.
Nitrate of soda 4946
Charcoal 9.63
Sulphur 8.31
Neptune Powder.
Nitro-glycerine 32.66 per cent.
Nitrate of soda 45-04
Charcoal 17.44
Sulphur 4.86
Ash 0.94
Miners' Powder Company Dynamite.
Nitro-glycerine 32.91 per cent.
Nitrate of soda 49-88
Charcoal, wood and partially charred wood 17.21
Ash 1.18
Brady's Dynamite or Vtdcan Powder.
Nitro-glycerine 33.00 per cent.
Nitrate of soda 50.00
Charcoal 10.00
Sulphur 7.00
It will be observed that all these powders are practically dynamites in which gunpowder is used in place of infusorial earth as the absorbent. In regard to the powder made by Michael Brady, Thomas Varney, a manufacturer of nitro-glycerine, dynamite, &c., testifies that it " belongs to a class which is now quite large and known as high explosive powder. Some of their names are Giant Powder, Mica Powder, Vulcan Powder, Jupiter Powder, Neptune Powder, Thunderbolt Powder, Hercules Powder, Titan Powder, Rend-Rock Powder, Vigorite Powder, Lithofracteur Dualin. "They are made by mixing nitro-glycerine with a dry pulverized substance, or mixture of substances such as have the capacity of taking up and holding a sufficient proportion of nitro-glycerine by absorption to make the mixture an effective explosive, and yet without being in such excess as to separate from the mass by leakage or compression, and at the same time the absorbent solids employed being such as will not chemically injure the proper explosive quality of the nitro-glycerine, and such as will render the mass practically inexplodible by concussions which ordinarily occur in handling and transportation. The solid ingredients, to-wit, the nitrate of soda, charcoal and sulphur, are first ground or otherwise pulverized, and dried if necessary.' The nitro-glycerine is then carefully mixed with them, so as to make a mass as nearly homogeneous as practicable, and the powder is then packed for market.
“In the manufacture of Vulcan powder there is a combination of nitro-glycerine with absorbent substances which are the equivalents of infusorial earth; and this combination constitutes an explosive compound, which has all the properties and qualities of the compound made by combining- nitro-glycerine with infusorial earth in making dynamite or Giant powder, or with mica scales in making Mica powder, or with mealed gunpowder in making Vulcan powder.
"In the first place, each of the materials used as absorbents in the Vulcan powder is solid. In the next place they are all free from any quality which will decompose, destroy or injure the nitro-glycerine. They are capable of pulverization. They are also dry, or may be made so. When pulverized each of them alone, or all of them in the proportions actually used, or in any other proportions, they will absorb and hold nitro-glycerine to the extent required by the patent sued upon, to-wit, enough to make an explosive powder without rendering the powder leaky, and without any explosive aid from the absorbents themselves.
"Dry pulverized nitrate of soda will thus hold 30 per cent, of nitroglycerine, charcoal 45 per cent., sulphur 30 per cent, (all these are explosive compounds), and when combined, as in Vulcan powder, they will thus hold 33 per cent."
After asserting that the absorbent of the Vulcan powder is similar to the infusorial earth in converting the liquid nitro-glycerine into the solid form, he adds : " The Vulcan powder absorbent, like that of the Neptune and Vigorite absorbents, has one quality not possessed by infusorial earth, to-wit, combustibility ; but this quality does not affect the powder as dynamite. Its only effect is to allow the absorbent to be burned by the heat of the exploding nitro-glycerine, thus adding gas and force to the explosion. Vulcan powder is no more combustible than dynamite of infusorial earth ; in fact, not as much so—that is, if an equal quantity of the two be set on fire, the Vulcan powder will burn the longest. Vulcan powder is practically as safe against concussion as infusorial earth dynamite.
"This particular class of powders, with combustible absorbents, has been made and sold by the complainant since the commencement of its business, which was in October, 1871. It had previously been made and sold by Alfred Nobel & Co. and by the Giant Powder Company, and by no other person or party prior to its use by them, to the best of my knowledge and belief. It has always been made
and sold by the two Giant Powder companies, under the name Giant Powder No. 2, and labelled as patented under the original dynamite patent of May 26, 1868, and its reissues. Nobel & Co. have always made and sold it as Dynamite No. 2. The two Giant Powder companies have made and sold more of No. 2 than of No. 1—meaning by No. I infusorial earth dynamite, or Giant powder. The nitrates of our No. 2 have always been those of potash or soda. It has been the same with Vulcan powder. Our carbons have been rosin, bituminous coal, pulverized wood or sawdust. These have been our favorite materials, but we have experimented with and tried in practice for a longer or shorter time many other things. As to charcoal, one of the earliest things tried, we found it not so good as several other things. As to sulphur, we long ago abandoned its use. In gunpowder to be burned by itself it is useful as facilitating ignition; but when combined with nitro-glycerine it is not needed for this purpose, as the absorbent is readily fired by the exploding nitro-glycerine. For absorbing it is no better than the nitrate, and not as good as charcoal, or any of the carbons or hydrocarbons used in absorbents. In other words, the sulphur in Vulcan powder is useless for any purpose except as an absorbent, and for that purpose would be better replaced by the same amount of nitrate and carbonaceous matter.
"The fine pulverization of the Vulcan absorbent is mainly for the purpose of increasing its absorbent capacity. Ordinary well-grained gunpowder will not safely take and hold over ten per cent, of nitroglycerine: but in the form of meal powder, its state before being grained, it will take and safely hold 45 to 50 per cent. The pulverization may be considered as having another advantage for purposes of absorbents, to-wit, the nitro-glycerine will be more intimately distributed in fine than in coarse materials, and the heat of the exploding oil will take effect quicker, and thus add force to the explosion.
"When Vulcan powder is exploded in practical use an exploder is always used. This exploder, by the force of its explosion, explodes the nitro-glycerine contained in the powder precisely as the nitro- ^
glycerine is exploded in No. 1 Dynamite. The explosion of the nitro-glycerine in No. 1 does not affect the infusorial earth, which is incombustible, but in No. 2 Neptune, Vigorite, Vulcan, &c., the nitroglycerine explosion produces high heat, which burns up the combustible absorbent. Any pulverized combustible would be consumed in like manner. Sawdust, charcoal, dried paper pulp, rosin, parafiine, pitch and other carbons or hydrocarbons which have been used in
making No. 2 are all completely consumed, just as is the Vulcan
absorbent."
Robert J. Howe, a dealer in powder and various explosives, and formerly foreman of the Laflin Powder Company's mills, testified for the defendants in the Neptune Powder Company case as follows: "Neptune powder compound, before adding nitro-glycerine, is in the form of powder dust, and is an explosive in itself. If ten percent., or any greater proportion of nitro-glycerine which it can retain, is added to it, the resulting compound is explosive, while infusorial earth must contain over thirty per cent, of nitro-glycerine to explode at all, and a much larger proportion to make an effective explosive. Grained gunpowder, mealed gunpowder, gunpowder dust or Neptune compound will not take up and retain more than about thirty percent. Difference in temperature makes a difference in the retentive power of the substances. They will retain more in cold weather than in warm. My experience teaches me that about thirty percent, of nitro-glycerine is the quantity they can be relied upon in practice to retain. Dry pulverized nitrate of soda will not take up and retain thirty per cent, of nitro-glycerine, but only about fifteen percent. It might be made to retain, under certain conditions of temperature, twenty percent., but when thirty percent, is added to it slowly trickles from it, and upon being squeezed in the hand it is discharged between the fingers.
"A mixture of 70 parts of either infusorial earth, charcoal or sawdust with 30 parts of nitro-glycerine is inexplosive, yet either of the following mixtures are explosive.
The nitro-glycerine does not receive explosive aid from the Neptune compound, from the gunpowder, from gunpowder dust and from a mixture of sawdust and nitrate of soda. It is a well-known fact that gunpowder is more effective when exploded by percussion caps than by simple fuse. Some consumers (contractors) always use percussion caps for that purpose. For the same reason, caps are better to explode Neptune powder, but Neptune powder is largely used by some parties and exploded (without cap) by fuse alone. In such use the powder of the Neptune powder explodes the nitro-glycerine of the Neptune powder in the same manner as indicated in the patent to Nobel, No. 50,617, filed loth May, 1865."
Dr. Henry Morton, President of the Stevens Institute, testified "That while at North Adams, in December, 1875, I mixed 52 parts of nitro-glycerine with 48 parts of infusorial earth sent me by the
complainants, and made this into a cartridge of the usual form, and inserted in this an 'exploder' or cap containing 16 grains of fulminating mercury. When this was fired in the usual way the cartridge did not explode. I then placed another ' exploder ' or cap containing 22 grains of the fulminate in the cartridge, and enclosed the whole in a short wrought-iron tube, tamping the ends with sand. On firing this ' exploder ' the iron tube was split open by the force of its explosion, but the mixture of infusorial earth and nitro-glycerine remained unaffected as before. I am, therefore, quite certain that a mixture of infusorial earth and nitro-glycerine in the proportions found by Dr. Hayes between the gunpowder and nitro-glycerine in the explosive compound of defendants, would be totally inexplodible."
Prof. Morton then goes on to show that using various devices for increasing the explosive force of gunpowder is no new thing and cites the following: "In the Chemical News, London, July 6, 1866, on
p. 16, he finds as follows : Some experiments were in the first instance made with gunpowder the grains of which had been saturated with nitro-glycerine. This powder burned much as usual, but with a
brighter flame in open air. When confined in shells or blast holes, greater effects were, however, produced with it than with ordinary gunpowder ; its destructive action is described as having been from three to six times greater than that of powder.
"The same account is published in the Proceedings of the Royal Institution, Vol. IV, p. 621, London, 1866. It is also published in the Journal of the Franklin Institute, Philadelphia, 1866, Vol. 52, p. 275.
"This deponent further says, that the increasing of the explosive force of gunpowder by the admixture of various bodies with it has been from time to time practiced from the early part of this century ;
thus, in the Encyclopedia Britannica, Edinburgh, 1815, is found an account of experiments made by Count Rumford. He used oil of turpentine, quicksilver, salt of tartar, sal ammoniac and brass tilings, with this object. In Cutbush's Pyroteclmy, Philadelphia, 1825, p. 140, we find : Quicklime is said to increase the force of powder. Dr. Baine says that three ounces of pulverized quicklime being added to
one pound of gunpowder, its force will be augmented one-third. M. Vergnaud, in a work on fulminating powders in 1846, asserts that certain rifle powder consisted of gunpowder mixed with fulminate of mercury. In the Mechanics Magazine, London, 1825, Vol. 3, p. 275, we find a description of experiments with powder mixed with oil, which showed an increase of effect. In Ure's Dictionary, New York, 1853, p. 174, we find admixture of sawdust with gunpowder recommended as increasing its explosive force. In the London Artizan of 1862 we have a description of Mr. Bennet's improved blasting powder, which consisted of a mixture in which lime was added to the usual ingredient of gunpowder. In the American Repertory, New York, 1841, Mr. Mayer proposes admixture of rosin with gunpowder to increase its effect in blasting."
The injunctions against the manufacturers of Neptune and Vulcan powders were granted. The value of this monopoly may be shown as follows : It is claimed that with proper exploders a dynamite composed of 30 per cent, nitro-glycerine and 70 per cent, meal powder will do as much work as a dynamite composed of 75 per cent, of nitroglycerine and 25 per cent, of infusorial silica.
The Popular Science News, James R. Nichols, M. D., editor, 17, 53, May 1883, contains an editorial article entitled, "What is Dynamite?” from which we extract the following as being a good example of popular science. Referring to the recent difficulties in England, Russia, Spain and elsewhere in Europe, it says : "In dynamite we have a pasty black mass, almost perfectly safe to handle, of which enough can be carried in a side pocket to destroy the lives of a hundred men, if favorably situated, or shatter a building nearly as effectively as could be done with half a barrel of gunpowder placed under it.
"What is dynamite? How is it manufactured? We are fully prepared to answer these questions, as we manufactured the first nitro-glycerine ever made in the United States, nearly twenty years ago, and have had some experiences with it not pleasant to recall. Dynamite is simply nitro-glycerine mixed with an adulterant to render it safe to transport. The added ingredient is usually a fine earth of great absorbent capacity. It has been found that the best kind is the earth which good housewives use to polish their silver with, properly called infusorial earth, because it is made up of the fossil remains of minute organisms. Dynamite, then, is a mixture of innocent polishing powder and sweet, bland glycerine, after it has been acted upon by nitric acid. There is nothing apparently very frightful in this mixture. We can eat glycerine on our puddings and griddle-cakes and grow fat upon it; and a box of silver polish in the house is as harmless as a cake of soap.
"In what has been stated, a strange law of chemical combination comes into view, a law by which, a vast change is produced in innocent bodies by a slight disturbance of their molecular constitution. We disturb the molecular constitution of glycerine by subjecting it to the action of nitric acid, by which nitrogen becomes a constituent of the body, and its whole chemical nature and relationship are changed.
"The dull, stupid nitrogen which exists so abundantly in the air, and which we breathe into our lungs every moment, day and night, becomes the agent which confers upon glycerine the most terrific powers possessed by any agent, save two, known to man. Does not this fact teach an impressive lesson as to the mystery of the forces of nature, and of man's capability of bringing them into action, and we may say, into subjection ? If such facts do not cause a feeling of respect for chemical science, it is difficult to conceive of any that will.
"In the manufacture of nitro-glycerine we simply mix with pure glycerine a certain proportion of sulphuric and nitric acids and stir the mixture until the reactions occur, which is in about twenty minutes. The vessels must be placed in freezing mixtures, for if at any time the temperature rises above 32° F. decomposition occurs, and if there is no explosion the whole mass goes off in a vast cloud of nitrous acid vapors which are troublesome and dangerous.
"We never ventured to act upon more than one hundred grains of glycerine at a time, and with this small amount the danger was great and accidents were not a few.
"Our method was to arrange upon a shelf, in a refrigerating mixture, twelve beaker glasses, each containing one hundred grains of glycerine, and into each of them the mixed acids were slowly allowed to enter, the thermometer being anxiously watched all the time. If the heat from the reactions rose above 32° in any glass, away would go the contents, filling the laboratory so densely with red fumes that no object could be seen six feet distant.
"It was regarded as a successful experiment if we saved four glasses out of the dozen. Whilst at present the methods of production are not different, the apparatus and appliances are greatly improved. It must be remembered that we were pioneers in the dangerous manufacture, and but little of the product was needed in medicine and the arts. Now the consumption is enormous, and large manufactories are established in many sections of the country. The United States government chemists make the best nitro-glycerine at the laboratory at Newport, Rhode Island. It is used largely for filling torpedoes.
"In what has been said we have endeavored to afford a popular view of the chemistry of dynamite. It does not explode at the touch of fire, as does gunpowder, but it must have brought to bear upon it, or in contact with it, another explosive agent, z. fulminate. A fulminate of mercury is better than a fulminate of silver, for the rhythm of its detonation is more in accord with that of dynamite. Dynamite detonates, and does not explode as does gunpowder. Its action is so much quicker than the movement of air that it strikes against a column of air with the same force as a hammer falling upon a blacksmith's anvil."
The following books may be of interest to students of explosives :
Die Grundsatze der Thermochemie. Dr. Hans Jahn. Vienna, 1882. Alfred Holder, 8vo, 238 pp.
Thermochemische Untersuchungen. Julius Thomsen. Vol. I. Neutralization und verwandte Phenomena, 449 pp. Vol. H. Metalloide, 506 pp. Leipzig, 1882. J. A. Barth.
Lehr- und Handbuch der Thermochemie. Dr. Alex. Naumann. Brunswick, 1882, F. Vieweg und Sohn. 606 pp.
The Explosive Art, 1875, and the Orders in Council of April 20, 1883, their Prejudicial Effect on Mining and Quarrying, and the Encouragement they give to Fenians. London, 1883, A. P. Blundell & Co.