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Expectorants

in pharmacy, medicines which favor the discharge of mucus from the windpipe and air-passages of the lungs.

EXPLOSIVES are substances which, by sudden decomposition or chemical action, produce large volumes of heated gas. The decomposition can be brought about by heat, by a blow or by other means. All explosives in actual use are those in which the chemical action is one of oxidation, the oxygen being supplied either by a nitrate or chlorate, nitric acid or an NO2 group. The ease with which an explosion can be brought about depends very largely on the physical condition of the explosive. For instance, gunpowder varies widely in its effects, according to the size of the particles composing the mixture. While the force of all explosives is increased by inclosing them in a small space, confinement is not necessary in the case of those compounds in which decomposition is very rapid, as, for instance, mercury fulminate.

FUSE CAMPING PRIMER CARTRIDGE A B STRING FIXING CARTRIDGE TO FUSE CAP MERCURY FULMINATE DYNAMITE EXPLOSIVES A. Blasting charge B. Cross section of primer In an article of this length it would be impossible to deal, even briefly, with all substances of an explosive nature, but as far as possible, representative types of all the well-known groups will be described. 1. Explosive mixtures, as distinct from explosive compounds, consist of two or more substances, at least one of which is a combustible, and at least one EXPLOSIVES of which is a supporter of combustion. at all or only a very small percentage. The ingredients of these mixtures are frequently not themselves explosives, but may be ordinary combustibles such as carbon, or sulphur, and stable salts such as chlorate or nitrate of potash. In the explosive powder, however, these otherwise harmless substances are incorporated so thoroughly, and are in such a fine state of division, that combustion can be induced almost instantaneously throughout the mass, with a consequent rapid evolution of hot gases, thus producing the phenomenon known as an explosion. The best known member of this class is gunpowder, now almost obsolete TANKS PICKING SHED EXPLOSIVES As substitutes for saltpeter, nitrates of sodium, barium, and ammonia have been employed, the latter extensively in the manufacture of "safety explosives" for use in mines.

Ammonal consists of a mixture of ammonium nitrate, aluminum and charcoal. Mixtures containing chlorates and perchlorates in place of nitrates have been manufactured and used to a considerable extent, but, owing to their unstable character, have never very largely replaced the nitrate mixtures. 2. Explosive compounds are those substances which are of such a nature as to DRYING ROOM NITRATION HOUSE A BC F G H I K BEATER HOUSE BOILING VATS L M PACKING HOUSE K EXPLOSIVES-DIAGRAM OF GUN-COTTON FACTORY A. Sulphuric acid B. Sulphuric acid C. Nitric acid D. Strong waste acid Key:

E. Mixed acids F. Oleum G. Water H. Teasing machine M. Sand trays for military purposes, but still largely used for sporting purposes, in mining, for fuses and for minor military purposes. It consists of a mixture of nitrate of potash (saltpeter), sulphur, and charcoal, the proportions varying somewhat, but being approximately fifteen parts of potassium nitrate to two parts of sulphur and three parts of charcoal. Great care is taken in selecting the sulphur, while the charcoal is prepared in special retorts, and the process of manufacture is one requiring much skilled supervision. Many modifications of gunpowder have been made from time to time. In place of charcoal, such materials as coal, coke, peat, sawdust, bran, sugar, starch and many others have been used, while powders have been produced containing either no sulphur Vol. IV-Cyc-F N. Poacher I. Endless belts J. Steam trays K. Nitration pans L. Beater be themselves explosive. Instead of a chemical reaction taking place between two separate substances, the reaction OCthe reaction occurs within the molecule of a single substance. As a consequence explosive compounds are more powerful in their action than mixtures, and modern explosives used in warfare all belong to this class.

For the most part they are produced by the nitration of organic compounds and the best known and most widely used is trinitrotoluene, commonly called T.N.T.

This is manufactured by the nitration of toluene in successive stages, mononitrotoluene being first produced, then dinitrotoluene, and finally , trinitrotoluene. It occurs as yellow crystals, yellow crystals , which darken on exposure to light, but is frequently used as a fused mass.

When held in a flame, it does not explode, EXPLOSIVES but burns with a smoky flame. It can, however, be detonated by means of fulminate of mercury. It is safe to handle and remarkably stable, and while slightly less powerful than picric acid it has the advantage that it does not attack metals or form unstable compounds with them.

Picric acid, or trinitrophenol, occurs as bright yellow crystals, but is usually fused when used as an explosive (v.

LYDDITE). Picric acid does not explode easily by direct percussion, but it can be readily detonated by mercury fulminate.

Nitroglycerin is prepared by nitrating glycerine in the presence of sulphuric acid. It is a heavy, oily liquid, having a specific gravity of 1.60. Owing to the EXPRESS Smokeless powders are mixtures of nitrocellulose or nitrocellulose nitroglycerin, with other ingredients added as "coolers." stabilizers, "deadeners," or "coolers."

The explosive is dissolved (usually in acetone or a mixture of ether alcohol), the mixture is rolled into sheets, the solvent evaporated, ted, and the powders finally dried at a temperature of about 40° C. Cordite belongs to this class, and consists of a mixture of nitroglycerin and guncotton, with a small amount of vaseline, gelatinized by means of acetone, and dried. Percussion caps are filled with explosive compositions, of which the chief constituent is mercury fulminate (Hg (CNO)2). When used alone, however, this substance is too rapid in its action STEAM BOILER MT MT NITRIC ACID STORE TANK SULPHURIC ACID STORE TANK TULUENE DISSOLVING PAN MT MT MT.

MT. MT MIXING PAN NITRATOR WASTE ACID WASTE ACID COOLING TANK TO DENITRATOR MT MEASURING TANK WASTE ACID EGG WASH TANK FILTER WATER TANK STEAM DIGESTER DRYING ROOM WASH 11 TANK FILTER EXPLOSIVES-DIAGRAM OF MANUFACTURE OF TRINITROTOLUENE (Τ.Ν.Τ.) great danger of premature explosion during transportation, nitroglycerin is no longer used as such. It forms, however, an important constituent of dynamite, which consists of nitroglycerin, absorbed on a base, which may be inert, combustible or explosive. The absorbents chiefly used are kieselguhr, magnesia, charcoal, and wood pulp. Explosive bases are usually nitrates of potassium, sodium, or ammonium or organic nitro derivatives. Guncotton, or trinitrocellulose, is manufactured by nitrating cotton with a mixture of nitric and sulphuric acids.

It is a grayish-white solid, odorless and tasteless, and, when properly prepared, is a safe and permanent explosive. and it is, therefore, mixed with such materials as potassium chlorate, sulphur, antimony sulphide, and powdered glass.

Other explosive compounds have been prepared by nitrating starch, sugar, dextrin, gelatin, resin, and even coal, but these are of minor importance.