Sulfurless gunpowder

Although the unique burning properties of gunpowder have ensured that the material continues to be used into the 21st century, there are occasions when a slower burning powder is required or when the presence of sulfur is unacceptable on the grounds of compatibility. 

Early versions of slow burning, sulfurless powders were brown in colour and known as Cocoa powder , the colour originating from an incompletely carbonised charcoal with a carbon level of about 50%. 

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

The above reaction corresponds to a composition containing saltpetre (87.1%) and charcoal (12.9%). 

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. 

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In manufacture, sulfurless gunpowders are available with a potassium nitrate content of 7(U80% and a charcoal level of 2(U30%. 

Chemical testing is carried out in an approved laboratory because the firework must first be dismantled. Wet methods of analysis are applied that involve analytical grade reagents to detect, in particular, the presence of chlorates in admixture with elemental sulfur. Sulfur-chlorate mixtures are banned in the UK, and one use of sulfurless gunpowder is in fireworks where chlorates are also present. 

Special types of gunpowders which contain no sulfur are known as sulfurless gunpowders. They are used where any corrosion due to sulfur is undesirable. The powders for pyro-devices are often of the sulfurless variety. 

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. 

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