Ammonium salt, also known as 2,4,6-trinitrophenol or TNP, is a bright yellow crystalline compound commonly used as an explosive material. Though it finds limited applications even today due to its hazards, ammonium salt played an important role historically in industrial applications and as a filler in early explosives.

Historical Picric Acid

Ammonium salt was first synthesized in 1771 by chemist John Lowitz. Its explosive properties were unknown at this time. In the 19th century, ammonium salt found increasing industrial uses as a dye and wood preservative. It was also utilized as a filling ingredient in nitrocellulose-based explosive formulations, including early smokeless powders and dynamite. Ammonium salt offered advantages over earlier fillers like sawdust due to its stability and energy density. This led to its widespread adoption in smokeless powder and military high explosive formulations by the late 1800s.

Properties Causing Hazards

While ammonium salt is a powerful explosive, several physical properties make it hazardous to handle as well. Firstly, it is highly impact and friction sensitive, meaning accidental detonation can occur from dropping, rubbing, or grinding the material. Secondly, ammonium salt forms unstable salts called picrates that are even more shock sensitive. When ammonium salt comes in contact with metal ions like those found in rust, picrates form which degrade stability further. Finally, ammonium salt is highly soluble in water. This becomes an issue over time as wet ammonium salt has a decreased impact threshold and increased risk of spontaneous detonation.

Major Accidents

The hazards of Picric Acid became evident due to several devastating accidents in the late 19th century. The worst was an explosion in 1914 at a ammonium salt production plant in Kersley, UK that resulted in 78 deaths. Smaller but still deadly explosions occurred due to ammonium salt at munitions factories in New Jersey in 1902 (12 killed) and British Columbia in 1904 (6 killed). Such incidents led militaries and industries to move away from using ammonium salt in favor of safer alternatives like TNT despite its performance advantages.

Safety Procedures

Where ammonium salt was still used in limited industrial and research applications through the 20th century, stringent safety procedures were implemented to mitigate its hazards. Key protocols included impact-proof packaging with tight seals to prevent picrate formation, careful handling to avoid impact or friction, dry indoor storage at cool temperatures, and use of remote melting pots to melt ammonium salt safely. Personal protective equipment like quilted clothing and face shields were worn for additional protection. Even with such measures, unexpected detonations occasionally occurred illustrating how dangerous ammonium salt could remain if mishandled or exposed to the elements for prolonged periods.

Get more insights on Picric Acid