Gunpowder compositions

Whilst the 75 15 10 formula corresponds to one of the quickest and most vigorous of the gunpowder compositions, a slower form is required for blasting (as detailed in Table 1.2). 

The basis data for internal ballistic calculations are thus obtained (also -> Ballistic Bomb - Burning Rate). As an example for the calculation of a double base gunpowder ) composition... 

In firework manufacture the use of gunpowder for priming pressed compositions containing chlorates can also be questioned on the grounds of chemical incompatibility. Sulfuric acid is known to react with chlorates to form chloric acid, HCIO3, which would be avoided by the use of sulfurless gunpowder. 

However, at the present time it appears that there is not a significant problem with the employment of sulfur gunpowder for the priming of chlorate compositions, and so the main use of sulfurless powders again rests with the military, particularly where igniter and priming compositions are in contact with magnesium. 

When black powder is used to propel rockets it is classed as a composite propellant (where the fuel and oxidiser are intimately mixed) and forms part of a rocket motor in which the powder is compressed to form a monolithic single grain inside a combustion chamber as shown in Figure 3.1. As well as gunpowder, the composite propellant mix will contain a binder which is used to improve the cohesion of the ingredients. Binders form a distinct phase and tend to reduce the sensitiveness of the propellant to shock and impact. When based on organic materials, as is normally the case, they will serve as part of the fuel component also. 

The constants "V and are dependent upon the chemical composition of the grains and their initial temperature. The burning rate equation (3.1) is based on the various empirical measurements and differs with the type of propellant. For one type of gunpowder the equation might be expressed as follows ... 

Although gunpowder remains the propellant of choice for the production of firework rockets, there has been development on military compositions since the beginning of the 19th century, notably in Europe. 

On ignition of the firework a reaction zone moves down the pressed composition and the components of the gunpowder react producing heat and hot gases. The latter entrain the titanium particles and eject them from the firework tube. During this process the metal particles are... 

More exotic effects call for more exotic materials, and considerable effort has gone into formulating compositions that are both spectacular in effect and safe to produce and handle. Thus a 30 mm fountain might contain mealed (or hue) gunpowder, potassium nitrate, sulfur, charcoal, antimony trisulhde, barium nitrate, hue aluminium and flitter aluminium with a dextrin binder. This composition is certainly a good deal more complicated than that used for sparklers but is relatively safe to produce and gives a good burst of white sparks. 

Thus, in summary, the composition can be divided into propellant, emitter and additives. The propellant is invariably gunpowder, whilst the emitter might be carbon, steel, iron, aluminium, magnesium/ aluminium alloy or even titanium. Additives are often used to promote the visual effects and to cheapen the composition. 

Some fountain compositions tend to be oxidant-rich due to the presence of excess potassium nitrate or sometimes various oxalates. The reason for this is to reduce the burning rate and/or to enhance the visual effects. Certainly if gunpowder is considered to be a mixture of fuels (charcoal and sulfur) and oxidant (potassium nitrate) then the maximum rate of burning should coincide with a slightly under-oxidised system. The burning rate is therefore reduced by adding excess nitrate to the system. 

Varying the ratios of the components must be done with a degree of caution however. With titanium compositions in particular there is a dehnite limit to the gunpowder/titanium balance beyond which the composition can explode during pressing the titanium flitters act as tiny razor blades which can friction ignite the gunpowder. 

The speed of burning of quickmatch is related to the chemical composition and the mass of the composition on the string. The linear burning rate equation enables a crude estimate of the speed of burning to be made. For example, a typical relationship already seen for gunpowder is given by equation (10.1),... 

Plastic Igniter Cord (PIC) is a modern version of quickmatch in which the gunpowder is replaced by a delay composition, consisting essentially of lead dioxide and silicon, while the support material is aluminium or iron wire. A plastic tube encloses the fuse, as in the manner of electrical... 

First, it must be understood that all fireworks and pyrotechnic compositions are classed as explosives. It is both dangerous and illegal (a) to manufacture gunpowder or pyrotechnic compositions, (b) to assemble such compositions into fireworks, (c) to dismantle (unmake) fireworks or (d) to import fireworks without giving required information to the Commissioners of Customs and Excise. 

There seems little doubt that the composition of gunpowder has been known in East from times of dimmest antiquity. The Chinese and Hindus contemporary with Moses are thought to have known of even the more recondite properties of the compound. It is very possible that Alexander the Great did absolutely meet with fire-weapons in India, which a passage in Quintus Curtius seems to indicate . 

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