The modern formula is C3H6N3O9, or

According to L'Hote, the oxygen is united with part of the nitrogen as protoxide. The heat liberated by the combustion is estimated to be twice as much as that of gunpowder; hence, while one volume of the latter yields in practice 200 volumes of cold gases, expanded by heat to 800 volumes, an equal weight of nitro-glycerine yields 1,298 volumes of gas, expanded to 10,384 volumes, giving 13 times the force of gunpowder. But the explosion takes in which 3 atoms of H have been replaced by 3 atoms of NO2. Its specific gravity is 1.6; and 100 parts yield on combustion: place much more suddenly than that of gunpow- der; hence the practical gain in effect is greater than the above figures show. The suddenness with which the force is developed renders nitro-glycerine unsuitable for ordnance. The very dangerous character of this material has led to various restrictions upon its transportation. It continues to be used in many places, and is prepared on the spot as it is required. In the Hoosac tunnel, Massachusetts, the United States works at Hallett's Point, New York, and at San Francisco, it was employed. Its insolubility in water and its liquid. form and high gravity render it very convenient for submarine operations and blasting in wet ground.

But its form brings a danger that portions of it, unexploded even in bore holes, may be scattered in rock fissures, or portions may be split accidentally, or may remain in vessels once filled, and afterward be exploded by accident. The proper way to get rid of it is to pour it into a running stream. To remove the great dangers connected with the preparation and transportation of this material, many propositions have been made, principally for mixing the oil with some substance (wood spirit, sulphate of zinc, lime or magnesia, etc.) which would render it inexplosive, and which could afterward be removed by simple means (e. g., by water) when the oil was to be used. None of these have come into use. When congealed it has been thought more dangerous than when •fluid; but this view is now contradicted by many practical authorities. Certainly careless handling and thawing of frozen nitro-glycerine has caused much loss of life and property. Through the pores or in the stomach, even in small quantities, this oil causes a terrible headache and colic.

Headache likewise results from inhaling the gases of its combustion; but all persons are not alike affected by these; and it is probable that most persons suffer little inconvenience from this cause when they have become accustomed to it.-Nobel introduced in Swedish quarries the practice of soaking common gunpowder with nitro-glycerine before blasting. The effect produced was very great; but this method was soon superseded by the invention of dynamite or giant powder, also introduced by Nobel. Dynamite is finely pulverized silex, or silicious ashes, or infusorial earth (most frequently the last), saturated with about three times its weight of nitro-glycerine, and constituting a mass resembling damp Graham flour. The pulverulent form prevents the transmission of ordinary sudden shocks, except under pressure in a confined space. The pressure of the inert mineral constituents serves also to absorb heat, so that a high temperature cannot be so easily imparted to the whole; but when imparted, this temperature effects a great expansion of the gases and increased effectiveness of explosion. Ignited in the open air, dynamite burns quietly with nitrous fumes.

Exploded (usually by means of a fulminating fuse or cap), it gives carbonic acid, nitrogen, and hydrogen, and leaves a white ash, with little or no smoke. Under favorable circumstances, the effectiveness of dynamite is equal or superior to that of nitro-glycerine; a fact not surprising, if it be remembered that the latter is liable to scatter unexploded drops, by reason of the maximum rapidity of its ignition. Dynamite is now generally recognized as the safest of all explosives. It is not affected by a prolonged temperature of 100° C, nor is it as dangerous as nitro-glycerine when it solidifies (at 8° 0.). Neither light nor electricity nor ordinary shocks cause it to decompose or explode. The principal dangers connected with its use are those of the strong fulminating powders used in the percussion fuses to explode it. It is also possible that if dynamite is carelessly made, it may contain an excess of nitro-glycerine, which, overcoming the capillary force of the mineral particles, may collect in drops and settle from the mass, becoming a source of serious accidents.

Moreover, it may be that freezing, or thawing after freezing, has a tendency to segregate the oil.-Dualline, introduced in 1869 by Lieut. Dittmar, is another nitro-glycerine powder, consisting probably (the exact composition is a secret) of Sehultze's wood gunpowder, saturated with this oil. Another formula is, in 100 parts, 50 of nitro-glycerine, 30 of fine sawdust, and 20 of nitre. It has been considerably used in Germany and the United States. As compared with dynamite (which it resembles in many respects), it has the advantage that it can be exploded under confinement with an ordinary blasting fuse; that it does not congeal so easily as dynamite; and that it is cheaper. As a disadvantage, Serlo mentions, that under some conditions it partially explodes, partially burns, and in this case produces noxious gases.-Improved lithofracteur, or lithofracteur-dynamite, manufactured by Krebs at Deutz near Cologne, is supposed to be the former lithofracteur saturated with nitro-glycerine. Another formula is, in 100 parts, 52 of nitro-glycerine, 30 of silex, 12 of stone coal, 4 of nitrate of soda, and 2 of sulphur. This would be a mixture of dynamite with a very bad gunpowder.

The safety and effectiveness of dynamite are claimed for this powder, with an additional advantage that it can bo exploded at much lower temperature -as low, according to some experiments, as -12° C.-Nobel has recently patented new nitro-glycerine powders, of different degrees of strength. The strongest consists of 68 parts nitrate of baryta and 12 parts rich bituminous coal, saturated with 12 parts nitro-glycerine. Nearly as powerful is a mixture of 70 parts nitrate of baryta, 10 parts resin, and 12 parts nitro-glycerine. The effect of each may be increased by adding 5 to 6 parts sulphur. They are exploded with percussion fuses.-Dr. Justus Fuchs, formerly in Nobel's employ, has proposed as an improvement on dynamite a compound containing 85 instead of 75 per cent. of nitro-glycerine, and instead of infusorial earth a chemically prepared substance, possessing greater absorbing power, and capable of complete combustion with almost no solid residue.-The Colonia powder, manufactured in Cologne, is said to be a black gunpowder, with 30 to 35 per cent. of nitro-glyeerine. It is exploded by artificial means only.- Chlorate of Potassa Powders. The property of acids containing large proportions of oxygen to part with it readily is strongly shown by chloric acid, HC103, in which the oxygen is very loosely held.