Chloropicrin is a poisonous, oily fluid with an extremely acrid smell. If humans come into contact with the substance they are likely to experience a blistering of the skin, irritation of the eyes and breathing difficulty. Chloropicrin fumes are especially dangerous, attacking the pulmonary veins in a victim's lungs when inhaled. The result: Pulmonary edema with gurgling breathing sounds and foamy red sputum, which, in extreme cases, can result in death.

The effects of chloropicrin were already well-known at the time of the First World War. Originally developed as a pesticide, Russia was able to weaponize the substance. The German army also began using it in gas grenades on the French front in 1916.

Now, more than a century later, the US State Department says the Russian army is using the substance once again, and Russian troops are rumored to be using other chemical weapons as well. The US Pentagon says the aim of such deployments is to dislodge Ukrainian troops from fortified positions in order to achieve tactical progress on the battlefield.

Should the US claim prove true, it would be a violation of the international Chemical Weapons Convention (CWC). In effect since 1997, the treaty bans the development, manufacture, stockpiling and use of chemical weapons. Moreover, it stipulated that all existing chemical weapons stockpiles be declared and destroyed under international supervision by 2012. Proof that this did not in fact happen was on full display in Syria, where the army of........

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