Gunpowder reaction

The red [SSNO] anion (9.2) (2max 448 nm) is produced by the reaction of an ionic nitrite with elemental sulfur or a polysulfide in acetone, DME or DMSO. ° The formation of 9.2 probably proceeds via an intermediate such as the [S2NO2] anion. This process is thought to occur in the gunpowder reaction, which also entails the reaction of potassium nitrite (produced by reduction of potassium nitrate with charcoal) and sulfur. 

Hence, the gunpowder reaction product, potassium carbonate, K2CO3, can be assigned the oxidation numbers K2( + 2) C( + 4) 0 (-6) on application of the above rules. 

Therefore the gunpowder reaction, which starts from solid components that evolve heat and form gases should be, and is, favoured thermodynamically, and is spontaneous. 

Table 2.4 Calculation of the sum of the enthalpies of the reaction products from gunpowder [reaction (2.8)] at two reference temperatures (2000 and 3000 K).

This type of explosive behaviour is not to be confused with explosions such as drat of gunpowder, where the explosion is caused by the extremely rapid expansion of the gases which are liberated by chemical reaction widr a large release of heat. 

In fact, most of the improvements to gunpowders after about 1600 ad concerned the methods of manufacture, there being no question that the proportions of the three components were correctly balanced for chemical reaction, that is to say stoichiometric . 

At room temperature, entropy effects are so small that they have little effect on the direction of a chemical reaction unless the difference in AG or 2s.H between reactants and products is correspondingly small. But at the high temperature encountered in pyrotechnic reactions such as the combustion of gunpowder, the relative importance of the change in entropy increases until it becomes a dominant factor. Hence, the importance of the temperature term in the free energy equation. 

The stoichiometric equation for the burning of sulfurless gunpowder has been given as in reaction (2.21)... 

The superiority of double-base propellant as compared to gunpowder is clearly reflected in the properties of the two products. For example the heat of reaction is about 900 as opposed to 700 calories g while the volume of gas produced is around 950 in comparison to 370 cm atm g at STP. The flame temperatures are listed as 3200 K and 2700 K respectively, while the specific impulse is about 1800 for smokeless propellant and bOONskg for gunpowder. 

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... 

The charcoal, or rather the coated charcoal, contributes to the fountain effect as does the gunpowder and aluminium by processes such as those described above. The flitter aluminium has a rather coarser particle structure than does the fine aluminium so that sparks from the former are longer lived and can survive a greater drop-height. Antimony trisulfide is commonly used to enhance the glittering effect in a series of chemical reactions with the gunpowder and aluminium. 

First, a simplified reaction for the gunpowder decomposition can be written as in reaction (7.1) ... 

From the above reaction the molar quantities associated with the combustion of a 2g charge of gunpowder can be listed as in Table 7.1. 

EQUATION (chemical) A representation of a chemical reaction, using the symbols of the elements to represent the actual atoms and molecules taking part in a reaction. For example, a classical, but simplified, overall reaction for the deflagration of gunpowder is as follows ... 

Gunpowder is simply a mixture of charcoal, sulfur, and potassium nitrate. Carbon and S react with 0 in the nitrate, and the N in the nitrate also releases heat in converting to N2 (the K combines with something to form the smoke). The reactions are approximately... 

Here is a simplified reaction equation for the combustion of gunpowder ... 

In this reaction 779 kcal/kg is evolved, the gas volume V0 amounts to 240 l./kg, and the calculated temperature is 2700°C. For mixture consisting of 70% potassium nitrate and 30% charcoal (Sulphurless Gunpowder SFG.I2) the heat of reaction is 670 20 kcal/kg, according to Thomas [27]. 

There are as many salts as there are acids and bases. Sodium cyanide, NaCN, is a deadly poison. Saltpeter, which is potassium nitrate, KN03, is useful as a fertilizer and in the formulation of gunpowder. Calcium chloride, CaCl2, is used ro deice roads, and sodium fluoride, NaF in toothpaste, prevents tooth decay. The acid-base reactions forming these salts are shown in Table 10.1. 

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