CHAMBERS'S INFORMATION FOR THE PEOPLE. 



Prismatic powder and pellet powder are granulated 

 by pressing the ' mill-cake ' into prismatic or 

 cylindrical moulds. The granulated powder is 

 dried in chambers heated by means of steam. 

 The dry powder is freed from dust by sifting in 

 a revolving cylinder lined with canvas, or fine 

 wire-gauze. 



The proportion of the ingredients in gunpowder 

 varies slightly, but there is, on the whole, a re- 

 markable agreement, as will be seen from the 

 following table : 



Nitre. Charcoal. Sulphur. 



British government powder...75 15 10 



French .. n ...75 12-5 12-5 



Prussian n n ...75 13-5 11-5 



Swedish -, . ...75 16 9 



We have said that this agreement is remarkable ; 

 it is so, because the proportion has been arrived 

 at purely empirically, and not from any theory of 

 the action of the ingredients upon one another 

 when the powder is fired. We are, indeed, igno- 

 rant of the exact nature of the chemical changes 

 which take place during the ignition of the powder. 

 We know that the oxygen of the nitre oxidises the 

 carbon, and, at least partially, the sulphur, and 

 that the gases given off consist chiefly of carbonic 

 acid, nitrogen, and carbonic oxide ; while the 

 solid residue, part of which remains in the gun as 

 fouling, the greater part escaping as smoke, con- 

 sists chiefly of sulphate of potash and carbonate 

 of potash. If these, the main products, were the 

 only products, the action might be represented by 

 the equation : 



I4KNO 3 + 48 + I2C = 4X3804 + 3K a CO 3 + SCO, 



+ 7N S + CO. 



But this would correspond to a gunpowder con- 

 taining in 100 parts, nitre, 83-8 ; charcoal, 8-5 ; 

 sulphur, 7-5 ; a proportion differing very consider- 

 ably from that found to be most advantageous. 



GUN-COTTON is formed by the action of a 

 mixture of strong nitric acid and strong sulphuric 

 acid upon cotton-wool (see CHEMISTRY). When 

 pure, its composition is C 6 H 7 (NO 2 ) 3 O 6 . In pre- 

 paring it, the greatest care requires to be taken 

 to wash the acids thoroughly out of it. This is 

 done in the manufacture of Abel's gun-cotton by 

 washing the skeins of gun-cotton in water, drying 

 in a centrifugal drying-machine, and reducing 

 the gun-cotton to a pulp in a rag-engine similar 

 to that used in paper-mills (see TEXTILE MANU- 

 FACTURES). The pulp is then beaten and washed 

 in a ' poaching-engine,' drained, and moulded in 

 any required form. Gun-cotton explodes at a 

 much lower temperature than gunpowder. The 

 latter requires a temperature of at least 600 F. 

 to explode it, while gun-cotton may explode at 

 277 F. and cannot, under any circumstances, 

 be heated to 400 F. without explosion. It has 

 some great advantages over gunpowder : i. It 

 can be stored wet with almost perfect safety, and 

 is as good as ever when dried again ; 2. It pro- 

 duces neither smoke nor fouling when fired ; 3. 

 It does not heat the gun so much as gunpowder. 

 On the other hand, the explosion is more rapid 

 than that of gunpowder, so that the barrel is more 

 strained. Gun-cotton is used for blasting, and 

 Abel's compressed gun-cotton, fired by means of 



352 



a detonating fuse, may be made use of for this- 

 purpose, even when unconfined that is, laid 

 loosely upon the mass which it is desired to> 

 break up. The detonating fuse used for this pur- 

 pose is a quill or thin metal tube containing a 

 few grains oi fulminate of mercury. 



Among the numerous other explosive sub- 

 stances, we shall only mention NITROGLYCERINE, 

 or GLONOIN-OIL. This is prepared from glyce- 

 rine (see CHEMISTRY) by the action of a mixture 

 of strong nitric acid and strong sulphuric acid r 

 and as it resembles gun-cotton in the mode of its 

 formation, it does so also in its constitution. Its- 

 formula is C 3 H (NO 2 ) 3 O 3 . It is a liquid heavier 

 than water, burns quietly when a light is applied 

 to a small quantity, but explodes with great 

 violence when struck or ignited by means of a 

 detonating fuse. Small quantities swallowed or 

 absorbed through the skin produce very severe 

 headache. As its liquid condition renders it in 

 many cases unsuitable for blasting, it is now often 

 used in the form of Dynamite, which is porous 

 earth (or the like) soaked with nitroglycerine. 



FULMINATES. Fulminate of mercury, or ful- 

 minating mercury, is prepared by dissolving 

 mercury in nitric acid, mixing the solution with 

 alcohol, and gently warming the mixture. The 

 salt crystallises out, and can be purified by re- 

 crystallisation. It is a white crystalline salt,, 

 having the composition C 2 HgN 2 O 2 . It explodes 

 with very great violence, when struck, when 

 heated, or when touched with strong sulphuric or 

 nitric acid. In the dry state it is an extremely 

 dangerous substance. Fulminate of silver can be 

 prepared in a similar way ; it is a much more 

 explosive and dangerous substance than the 

 fulminate of mercury. 



PERCUSSION CAPS are primed with a mixture 

 containing fulminate of mercury, chlorate of 

 potash, and either powdered glass or sulphide of 

 antimony. Only a small quantity of this mixture 

 is made at a time, on account of the danger of 

 explosion. 



LUCIFER MATCHES. Common lucifer matches 

 are tipped with a paste consisting of glue, in 

 which there are mixed phosphorus and some 

 substance which readily yields oxygen, such as 

 chlorate of potash, peroxide of manganese, or 

 peroxide of lead. When such a mixture is rubbed,, 

 the phosphorus takes fire. As it is difficult to- 

 kindle solid combustibles such as wood by means 

 of the flame of phosphorus, the match is dipped 

 in paraffin or sulphur, which, when volatilised by 

 the heat of the phosphorus flame, is easily kindled,, 

 and in its turn kindles the wood. 



SAFETY MATCHES, which ignite only when 

 rubbed on a specially prepared surface, are tipped 

 with a mixture of sulphide of antimony, chlorate 

 of potash, and powdered glass, made into a paste- 

 with glue. This mixture is very easily kindled,, 

 but not so easily as to take fire when rubbed on 

 any rough surface. The prepared surface is- 

 coated with a mixture of red or amorphous phos- 

 phorus (see CHEMISTRY) and powdered glass. 

 When the match is rubbed on this, a small 

 quantity of the red phosphorus takes fire, and 

 kindles the mixture with which the match is. 

 tipped. 



