Impact of Sodium Cyanide at the Tianjin Explosion Site
Impact of Sodium Cyanide at the Tianjin Explosion Site Officials investigating a huge explosion at a warehouse in Tianjin in China have discovered a store of 700 tonnes of sodium cyanide – more than 70 times the legal limit allowed. Cyanide has a particularly unpleasant reputation and finding it at a major disaster site is far from welcome. However, if officials act fast they should be able to limit its damaging effects.
What is sodium cyanide?
The term cyanide is clearly understood in the public consciousness to be almost synonymous with poison itself. This is largely because of its use as lethal suicide pill (L-pill) in World War 2, most notably with the suicide of Nazi army officer Erwin Rommel. The cyanide used in the L-pill was potassium cyanide but the properties of sodium cyanide are nearly identical.
An inorganic and very innocent looking white solid with deadly properties, sodium cyanide (NaCN) can be fatal at amounts as little as 5% of a teaspoon. It is produced from the equally dangerous gas hydrogen cyanide (HCN) in a simple process with sodium hydroxide.
Why would a company want so much of it?
Sodium cyanide is used industrially across the globe, most frequently in the mining of gold. Although most of us have the traditional imagery of a 19th-century gold miner panning for nuggets, this isn’t the industrial method used today.
Most of the world’s gold is not found in nugget form but as very fine gold powders in rocks. In fact, our cultural demand for gold forces us to mine in rocks that can be as low as 0.005% gold. This means we need industrial extraction to separate and purify gold from all the other materials.
After mining and milling, the crude rock mixture is turned into a fine powder and added to a solution of sodium cyanide. The gold forms strong bonds with cyanide molecules and can then be separated from the rest of the minerals because it is then soluble in water. It then reacts with zinc and turns back into a solid. Finally is smelted to isolate the gold and cast into bars.
How dangerous is it?
As with the very similar potassium cyanide used in the L-pill, sodium cyanide is extremely toxic to humans. Although there are risks with skin absorption, the biggest risk is ingestion. Inhaling or swallowing sodium cyanide blocks oxygen transport causing serious medical problems and ultimately death.