[Illustration: META-DINITRO-BENZENE No.2]
by treating a substance known as mannite, C_{6}H_{8}(OH)_{6}, an alcohol formed by the lactic acid fermentation of sugar and closely related to the sugars, with nitric and sulphuric acids. It is a solid substance, and very explosive; it contains 18.58 per cent. of nitrogen.
Nitro-starch has also been used for the manufacture of an explosive. Muhlhauer has described (Ding. Poly. Jour., 73, 137-143) three nitric ethers of starch, the tetra-nitro-starch, C_{12}H_{16}O_{6}(ONO_{2})_{4}, the penta- and hexa-nitro-starch. They are formed by acting upon potato starch dried at 100° C. with a mixture of nitric and sulphuric acids at a temperature of 20° to 25° C. Rice starch has also been used in its production. Muhlhauer proposes to use this body as a smokeless powder, and to nitrate it with the spent mixed acids from the manufacture of nitro- glycerine. This substance contains from 10.96 to 11.09 per cent. of nitrogen. It is a white substance, very stable and soluble even in cold nitro-glycerine.
The explosive bodies formed by the nitration of jute have been studied by Messrs Cross and Bevan. and also by Mühlhäuer. The former chemists give jute the formula C_{12}H_{18}O_{9}, and believe that its conversion into a nitro-compound takes place according to the equation—
C_{12}H_{18}O_{9} + 3HNO_{3} = 3H_{2}O + C_{12}H_{15}O_(6}(NO_{3})_{3}.
This is equivalent to a gain in weight of 44 per cent. for the tri- nitrate, and 58 per cent. for the tetra-nitrate. The formation of the tetra-nitrate appears to be the limit of nitration of jute fibre. Messrs Cross and Bevan say, "In other words, if we represent the ligno-cellulose molecule by a C_{12} formula, it will contain four hydroxyl (OH) groups, or two less than cellulose similarly represented." It contains 11.5 per cent. of nitrogen. The jute nitrates resemble those of cellulose, and are in all essential points nitrates of ligno-cellulose.
Nitro-jute is used in the composition of the well-known Cooppal Smokeless Powders. Cross and Bevan are of opinion that there is no very obvious advantage in the use of lignified textile fibres as raw materials for explosive nitrates, seeing that a number of raw materials containing cellulose (chiefly as cotton) can be obtained at from £10 to £25 a ton, and yield also 150 to 170 per cent. of explosive material when nitrated (whereas jute only gives 154.4 per cent.), and are in many ways superior to the products obtained from jute. Nitro-lignin, or nitrated wood, is, however, largely used in the composition of a good many of the smokeless powders, such as Schultze's, the Smokeless Powder Co.'s products, and others.
~The Danger Area.~—That portion of the works that is devoted to the actual manufacture or mixing of explosive material is generally designated by the term "danger area," and the buildings erected upon it are spoken of as "danger buildings." The best material of which to construct these buildings is of wood, as in the event of an explosion they will offer less resistance, and will cause much less danger than brick or stone buildings. When an explosion of nitro-glycerine or dynamite occurs in one of these buildings, the sides are generally blown out, and the roof is raised some considerable height, and finally descends upon the blown-out sides. If, on the other hand, the same explosion had occurred in a strong brick or stone building, the walls of which would offer a much larger resistance, large pieces of brickwork would probably have been thrown for a considerable distance, and have caused serious damage to surrounding buildings.
It is also a very good plan to surround all danger buildings with mounds of sand or earth, which should be covered with turf, and of such a height as to be above the roof of the buildings that they are intended to protect (see frontispiece).[A] These mounds are of great value in confining the force of the explosion, and the sides of the buildings being thrown against them are prevented from travelling any distance. In gunpowder works it is not unusual to surround the danger buildings with trees or dense underwood instead of mounds. This would be of no use in checking the force of explosion of the high explosives, but has been found a very useful precaution in the case of gunpowder.
[Footnote A: At the Baelen Factory, Belgium, the danger buildings are erected on a novel plan. They are circular in ground plan and lighted entirely from the roof by means of a patent glass having wire-netting in it, and which it is claimed will not let a splinter fall, even if badly cracked. The mounds are then erected right up against the walls of the building, exceeding them in height by several metres. For this method of construction it is claimed that the force exerted by an explosion will expand itself in a vertical direction ("Report on Visits to Certain Explosive Factories," H.M. Inspectors, 1905).]