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EPONITE

A decolourizing char in the nature of a vegetable soot, containing about 82 per cent, of carbon, the decolourizing efficiency of which is increased, according to C. F. Bardos, by addition of 30 to 50 per cent, of charred sawdust.

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EXPLOSIVES

Explosives are substances which, under the influence of heat or shock, or both, are instantly resolved into gases occupying at the high temperature of explosion comparatively enormous volumes, and consequently exert ing tremendous pressure, which disrupts the objective or drives projectiles out of guns. They may be said to consist of bodies such as nitroglycerine and nitrocellulose, which are explosive in themselves, or mixtures of substances which, separately, are or may be nonexplosive, but when intimately mixed are capable of being exploded either by ignition or detonators. Gunpowder is a mechanical mixture of nitre, or Chili nitre, charcoal, and sulphur in proportions of about 75, 15, and 10 respectively, and is still largely employed for blasting purposes, although it has ceased to be used as a military propellant, or nearly so. Its explosive power is due to an enormous evolution of gas from a relatively small quantity of solid substance. The nitre supplies the oxygen necessary for burning up the carbon and the sulphur, at the same time yielding nitrogen gas, It is a socalled “low explosive,” while the “high explosives” have a velocity of explosion some 500 times greater. These high explosives are rich in nitrogen, and when detonated, furnish large quantities of that gas and others which are enormously expanded by the heat generated by the chemical changes which take place, so that they amount to from 10,000 to 15,000 times the volume of the explosive substance itself. Just as nitre supplies the oxygen necessary to burn the charcoal and sulphur contained in gunpowder, so hydrogen is removed from cotton, glycerine, phenol, toluene, etc., and is substituted by groups of the radical NOa, which contain and supply the oxygen essential to the combustion of the associated carbon and hydrogen, the carbon being converted into gaseous oxides and the hydrogen into steam, while at the same time, the nitrogen is also set free in the torm of gas. Some of these substances, and their nitrated forms, may be roughly indicated as follows: Cellulose is chemically changed into nitrocellulose or guncotton ef 2C6H10O5 + 6HNO3 = C12HmO108 + 6HjO. Glycerine becomes changed to nitroglycerine

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EMERALD

A double silicate of aluminium and glucinum, or green variety of beryl, being a gem found in mineral form.

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EAU DE JAVELLE

A dilute solution of sodium hypochlorite at one time commonly used in France for bleaching and disinfecting purposes. It can be prepared by treating a solution of calcium hypochlorite with one of sodium carbonate and filtering off the precipitated calcium carbonate.

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ENAMELLED IRON

Iron plates are enamelled by coating them, after cleaning, with alkaline silicates containing borates, and then firing them.

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ERGOT OF RYE

A fungoid growth on the seeds of the common rye, containing an active principle named ergotine, in the nature of a yellow crystalline alkaloid soluble in alcohol and ether, which possesses narcotic properties, and is used in medicine. The formula CgsHjoNjOg is sometimes assigned to it.

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ETHANE or ETHYL HYDRIDE

A gaseous hydrocarbon constituent of crude petroleum.

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EMBOLITE

A mineral chlorobromide of silver found in Arizona, Colorado, New Mexico, and Chile, having the composition Ag5Cl3I3r2 or Ag.

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ESPARTO GRASS

A strong tufty wild grass which grows abundantly in Spain and Algeria, and is largely used in the manufacture of cordage and paper. It is boiled with caustic soda to dissolve the fleshy parts, then bleached. A wax, amounting to 3 J per cent., is obtained as a byproduct. The trade is very large, amounting to more than 200,000 tons per annum.

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EBULLIOSCOFE

A form of apparatus for determining the boilingpoints of liquids.

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