N.X

n.x, which maybe some compound of diazobenzene. probably the most vigorous high explosive at present known is the substance called hydrazoic acid or azoimide (q.v.). it forms salts with metals such as agn3, which explode in a peculiar manner. the ammonium compound, nh4n3, may become a practical explosive of great value. mercuric fulminate, hgc2n2o2, is one of the most useful high explosives known. it is formed by the action of a solution of mercurous nitrate, containing some nitrous acid, on alcohol. it is a white crystalline substance almost insoluble in cold water and requiring 130 times its weight of boiling water for solution. it may be heated to 180 deg. c. before exploding, and the explosion so brought about is much milder than that produced by percussion. it forms the principal ingredient in cap compositions, in many fuses and in detonators. in many of these compositions the fulminate is diluted by mixture with certain quantities of inert powders so that its sensitiveness to friction or percussion is just so much lowered, or slowed down, that it will fire another mixture capable of burning with a hot flame. for detonating dynamite, guncotton, &c., it is generally employed without admixture of a diluent. _smokeless propellants._--gunpowders and all other explosive mixtures or compounds containing metallic salts must form smoke on combustion. the solids produced by the resolution of the compounds are in an extremely finely-divided state, and on being ejected into the atmosphere become more or less attached to water vapour, which is so precipitated, and consequently adds to the smoke. the simplest examples of propellants of the smokeless class are compressed gases. compressed air was the propellant for the zalinski dynamite gun. liquefied carbon dioxide has also been proposed and used to a slight extent with the same idea. it is scarcely practical, however, because when a quantity of a gas liquefied by pressure passes back again into the gaseous state, there is a great absorption of heat, and any remaining liquid, and the containing vessel, are considerably cooled. steam guns were tried in the american civil war in 1864; but a steam gun is not smokeless, for the steam escaping from the long tube or gun immediately condenses on expansion, forming white mist or smoke. at the earliest stage of the development of guncotton the advantage of its smokeless combustion was fully appreciated (see guncotton). that it did not at once take its position as _the_ smokeless propellant, was simply due to its physical state--a fibrous porous mass--which burnt too quickly or even detonated under the pressure required in fire-arms of any kind. in the early eighties of the 19th century it was found that several substances would partly dissolve or at least gelatinize guncotton, and the moment when guncotton proper was obtained as a colloid or jelly was the real start in the matter of smokeless propellants. guncotton is converted into a gelatinous form by several substances, such as esters, e.g. ethyl acetate or benzoate, acetone and other ketones, and many benzene compounds, most of which are volatile liquids. on contact with the guncotton a jelly is formed which stiffens as the evaporation of the gelatinizing agent proceeds, and finally hardens when the evaporation is complete. whilst in a stiff pasty state it may be cut, moulded or pressed into any desired shape without any danger of ignition. in fact guncotton in the colloid state may be hammered on an anvil, and, as a rule, only the portion struck will detonate or fire. guncotton alone makes a very hard and somewhat brittle mass after treatment with the gelatinizing agent and complete drying, and small quantities of camphor, vaseline, castor oil and other substances are incorporated with the gelatinous guncotton to moderate this hard and brittle state. all the smokeless powders, of which gelatinized guncottons or nitrated celluloses are the base, are moulded into some conveniently shaped grain, e.g. tubes, cords, rods, disks or tablets, so that the rate of burning may be controlled as desired. the vieille powder, invented in 1887 and adopted in france for a magazine rifle, consisted of gelatinized guncotton with a little picric acid. later a mixture of two varieties of guncotton gelatinized together was used. in addition to guncottons other explosive or non-explosive substances are contained in some of these powders. guncotton alone in the colloid state burns very slowly if in moderate-sized pieces, and when subdivided or made into thin rods or strips it is still very mild as an explosive, partly from a chemical reason, viz. there is not sufficient oxygen in it to burn the carbon to dioxide. many mixtures are consequently in use, and many more have been proposed, which contain some metallic salt capable of supplying oxygen, such as barium or ammonium nitrate, &c., the idea being to accelerate the rate of burning of the guncotton and if possible avoid the production of smoke. the discovery by a. nobel that nitroglycerin could be incorporated with collodion cotton to form blasting gelatin (see dynamite) led more or less directly to the invention of ballistite, which differs from blasting gelatin only in the relative amounts of collodion, or soluble nitrated cotton, and nitroglycerin. ballistite was adopted by the italian government in 1890 as a military powder. very many substances and mixtures have been proposed for smokeless powder, but the two substances, guncotton and nitroglycerin, have for the most part kept the field against all other combinations, and for several reasons. nitroglycerin contains a slight excess of oxygen over that necessary to convert the whole of the carbon into carbon dioxide; it burns in a more energetic manner than guncotton; the two can be incorporated together in any proportion whilst the guncotton is in the gelatinous state; also all the liquids which gelatinize guncotton dissolve nitroglycerin, and, as these gelatinizing liquids evaporate, the nitroglycerin is left entangled in the guncotton jelly, and then shares more or less its colloidal character. in burning the nitroglycerin is protected from detonation by the gelatinous state of the guncotton, but still adds to the rate of burning and produces a higher temperature. _desirable qualities._--smokelessness is one only of the desirable properties of a propellant. all the present so-called smokeless powders produce a little fume or haze, mainly due to the condensation of the steam which forms one of the combustion products. there is often also a little vapour from the substances, such as oils, mineral jelly, vaseline or other hydrocarbon added for lubrication or to render the finished material pliable, &c. the gases produced should neither be very poisonous nor exert a corrosive action on metals, &c. the powder itself should have good keeping qualities, that is, not be liable to chemical changes within ordinary ranges of temperature or in different climates when stored for a few years. in these powders slight chemical changes are generally followed by noticeable ballistic changes. all the smokeless powders of the present day produce some oxide of nitrogen, traces of which hang about the gun after firing and change rapidly into nitrous and nitric acids. nitrous acid is particularly objectionable in connexion with metals, as it acts as a carrier of oxygen. the fouling from modern smokeless powders is a slight deposit of acid grease, and the remedy consists in washing out the bore of the piece with an alkaline liquid. the castor oil, mineral jelly or camphor, and similar substances added to smokeless powders are supposed to act as lubricants to some extent. they are not as effective in this respect as mineral salts, and the rifling of both small-arms and ordnance using smokeless powders is severely gripped by the metal of the projectile. the alkaline fouling produced by the black and brown powders acted as a preventive of rusting to some extent, as well as a lubricant in the bore. _danger in manufacture._--in the case of the old gunpowders, the most dangerous manufacturing operation was incorporation. with the modern colloid propellants the most dangerous operations are the chemical processes in the preparation of nitroglycerin, the drying of guncotton, &c. after once the gelatinizing solvent has been added, all the mechanical operations can be conducted, practically, with perfect safety. this statement appears to be correct for all kinds of nitrated cellulose powders, whether mixed with nitroglycerin or other substances. should they become ignited, which is possible by a rise of temperature (to say 180 deg.) or contact with a flame, the mixture burns quickly, but does not detonate. as a rule naval and military smokeless powders are shaped into flakes, cubes, cords or cylinders, with or without longitudinal perforations. all the modifications in shape and size are intended to regulate the rate of burning. sporting powders are often coloured for trade distinction. some powders are blackleaded by glazing with pure graphite, as is done with black powders. one object of this glazing is to prevent the grains or pieces becoming joined by pressure; for rods or pieces of some smokeless powders might possibly unite under considerable pressure, producing larger pieces and thus altering the rate of burning. most smokeless powders are fairly insensitive to shock. all these gelatinized powders are a little less easily ignited than black powders. a slightly different cap composition is required for small-arm cartridges, and cannon cartridges generally require a small primer or starter of powdered black gunpowder. it is desired that a propellant shall produce the maximum velocity with the minimum pressure. the pressure should start gently so that the inertia of the projectile is overcome without any undue local strain on the breech near the powder chamber, and more especially that as more and more space is given to the gases by the movement of the projectile up the gun to the muzzle, gas should be produced with sufficient rapidity to keep the pressure nearly uniform or slightly increasing along the bore. the leading idea for improvements in relation to propellants is to obtain the greatest possible pressure regularly developed, and at the same time the lowest temperatures. (w. r. e. h.) _law._--in 1860 an act was passed in england "to amend the law concerning the making, keeping and carriage of gunpowder and compositions of an explosive nature, and concerning the manufacture and use of fireworks" (23 & 24 vict. c. 139), whereby previous acts on the same subject were repealed, and minute and stringent regulations introduced. amending acts were passed in 1861 and 1862. in 1875 was passed the explosives act (38 & 39 vict. c. 17), which repealed the former acts, and dealt with the whole subject in a more comprehensive manner. this act, containing 122 sections, and applying to scotland and ireland, as well as to england, constitutes, with various orders in council and home office orders, a complete code. the act of 1875 was based on the report of a committee of the house of commons, public opinion having been greatly excited on the subject by a terrible explosion on the regent's canal in 1874. explosives are thus defined: (1) gunpowder, nitroglycerin, dynamite, guncotton, blasting powders, fulminate of mercury or of other metals, coloured fires, and every other substance, whether similar to those above-mentioned or not, used or manufactured with a view to produce a practical effect by explosion or a pyrotechnic effect, and including (2) fog-signals, fireworks, fuses, rockets, percussion caps, detonators, cartridges, ammunition of all descriptions, and every adaptation or preparation of an explosive as above defined. part i. deals with gunpowder, providing that it shall be manufactured only at factories lawfully existing or licensed under the act; that it shall be kept (except for private use) only in existing or new magazines or stores, or in registered premises, licensed under the act. private persons may keep gunpowder for their own use to the amount of thirty pounds. the act also prescribes rules for the proper keeping of gunpowder on registered premises. part ii. deals with nitroglycerin and other explosives; part iii. with inspection, accidents, search, &c.; part iv. contains various supplementary provisions. by order in council the term "explosive" may be extended to any substance which appears to be specially dangerous to life or property by reason of its explosive properties, or to any process liable to explosion in the manufacture thereof, and the provisions of the act then extend to such substance just as if it were included in the term "explosive" in the act. the act lays down minute and stringent regulations for the sale of gunpowder, restricting the sale thereof in public thoroughfares or places, or to any child apparently under the age of thirteen; requiring the sale of gunpowder to be in closed packages labelled; it also lays down general rules for conveyance, &c. the act also gives power by order in council to define, from time to time, the composition, quality and character of any explosive, and to classify explosives, and such orders in council are frequently made including new substances; those in force will be found in the _statutory rules and orders_, tit. "explosive substance." the merchant shipping act 1894 imposes restrictions on the carriage of dangerous goods in a british or foreign vessel, "dangerous goods" meaning aquafortis, vitriol, naphtha, benzine, gunpowder, lucifer matches, nitroglycerin, petroleum and any explosive within the meaning of the explosives act 1875. the act is administered by the home office, and an annual report is published containing the proceedings of the inspectors of explosives and an account of the working of the act. each annual report gives a list of explosives at the time authorized for manufacture or importation, and appendices containing information as to accidents, experiments, &c. practically every european country has legislated on the lines of the english act of 1875, austria taking the lead, in 1877, with an explosives ordinance almost identical with the english act. the united states and the various english colonies also have explosives acts regulating the manufacture, storage and importation of explosives. (see also petroleum.) (t. a. i.) bibliography.--m. berthelot, _sur la force des matieres explosives_ (paris, 1883); p.f. chalon, _les explosifs modernes_ (paris, 1886); w.h. wardell, _handbook of gunpowder and guncotton_ (london, 1888); j.p. cundill, _a dictionary of explosives_ (london, 1889 and 1897); m. eissler, _a handbook of modern explosives_ (london, 1896, new ed. 1903); j.a. longridge, _smokeless powder and its influence on gun construction_ (london, 1890); c. napier hake and w. macnab, _explosives and their power_ (london, 1892); g. coralys, _les explosifs_ (paris, 1893); a. ponteaux, _la poudre sans fumee et les poudres anciennes_ (paris, 1893); f. salvati, _vocabolario di polveri ed explosivi_ (rome, 1893); c. guttmann, _the manufacture of explosives_ (london, 1895 and later); s.j. von romocki, _geschichte der sprengstoffchemie, der sprengtechnik und des torpedowesens bis zum beginn der neusten zeit_ (berlin, 1895); _geschichte der explosivstoffe, die rauchschwachen pulver_ (berlin, 1896); p.g. sanford, _nitro-explosives_ (london, 1896); l. gody, _traite theorique et pratique des matieres explosives_ (namur, 1896); r. wille, _der plastomerite_ (berlin, 1898); e. sarrau, _introduction a la theorie des explosifs_ (1893); _theorie des explosifs_ (1896); o. guttmann, _manufacture of explosives_ (london, 1895); e.m. weaver, _notes on military explosives_ (new york, 1906); m. eissler, _the modern high explosives_ (new york, 1906); _treatise on service explosives_, published by order of the secretary of state for war (london, 1907). most of the literature on modern explosives, e.g. dynamite, &c., is to be found in papers contributed to scientific journals and societies. an index to those which have appeared in the _journal of the society of chemical industry_ is to be found in the decennial index (1908) compiled by f.w. renant. footnote: [1] not necessarily heat energy entirely. a number of substances--acetylides and some nitrogen compounds, such as nitrogen chloride--decompose with extreme violence, but _little heat_ is produced. express (through the french from the past participle of the lat. _exprimere_, to press out, by transference used of representing objects in painting or sculpture, or of thoughts, &c. in words), a word signifying that which is clearly and definitely set forth or represented, explicit, and thus used of a meaning, a law, a contract and the like, being specially contrasted with "implied." thus in law, malice, for which there is actual evidence, as apart from that which may be inferred from the acts of the person charged, is known as "express." the word is most frequently used with the idea of something done with a definite purpose; the term "express train," now meaning one that travels at a high speed over long distances with few intermediate stoppages, was, in the early days of railways, applied to what is now usually called a "special," i.e. a train not running according to the ordinary time-tables of the railway company, but for some specific purpose, or engaged by a private person. about 1845 this term became used for a train running to a particular place without stopping. similarly in the british postal service, express delivery is a special and immediate delivery of a letter, parcel, &c., by an express messenger at a particular increased rate. the system was adopted in 1891. in the united states of america, express companies for the rapid transmission of parcels and luggage and light goods generally perform the function of the post office or the railways in the united kingdom and the continent of europe. not only do they deliver goods, but by the cash on delivery system (see cash) the express companies act as agents both for the purchaser and seller of goods. they also serve as a most efficient agency for the transmission of money, the express money order being much more easily convertible than the postal money orders, as the latter can only be redeemed at offices in large and important towns. the system dates back to 1839, when one william frederick harnden (1813-1845), a conductor on the boston and worcester railway, undertook on his own account the carrying of small parcels and the performance of small commissions. obliged to leave the company's service or abandon his enterprise, he started an "express" service between boston and new york, carrying parcels, executing commissions and collecting drafts and bills. alvin adams followed in 1840, also between boston and new york. from 1840 to 1845 the system was adopted by many others between the more important towns throughout the states. the attempt to carry letters also was stopped by the government as interfering with the post office. in 1854 began the amalgamation of many of the companies. thus under the name of the adams express company the services started by harnden and adams were consolidated. the lines connecting the west and east by albany, buffalo and the lakes were consolidated in the american express company, under the direction of william g. fargo (q.v.), henry wells and johnston livingston, while another company, wells, fargo & co., operated on the pacific coast. the celebrated "pony express" was started in 1860 between san francisco and st joseph, missouri, the time scheduled being eight days. the service was carried on by relays of horses, with stations 25 m. apart. the charge made for the service was $2.50 per 1/2 oz. the completion of the pacific telegraph company line in 1861 was followed by the discontinuance of the regular service. the name "express" is applied to a rifle having high velocity, flat trajectory and long fixed-sight ranges; and an "express-bullet" is a light bullet with a heavy charge of powder used in such a rifle (see rifle).