Phosphorus trichloride

Phosphorus trichloride is an inorganic compound made up of one phosphorus atom and three chlorine atoms. On first sight, you may mistake the clear, colorless liquid for water, but if you drink it, you will die shortly. It is actually considered to be a nerve agent precursor, a highly toxic chemical upon contact with the skin or the respiratory system.

Properties
Phosphorus trichloride is made up of two different elements, one phosphorus atom along with three chlorine atoms. In this compound, phosphorus takes on an oxidation number of +3, while chlorine's oxidation number is what it almost always stays at, -1. Phosphorus trichloride is a colorless (or slightly yellow) fuming liquid that gives off a pungent odor similar to that of hydrochloric acid. Phosphorus trichloride is not a pleasant substance. It is as vile as it smells, causing severe burns on skin and eyes if contacted. It is also considered toxic by inhalation, ingestion, and skin absorption. When it comes in contact with water, phosphorus trichloride reacts violently and forms hydrochloric acid, which becomes apparent as white fumes and is also very toxic. In addition to water, phosphorus trichloride also reacts explosively with acetic acid, aluminum, chromyl chloride, diallyl phosphite, allyl alcohol, dimethyl sulfoxide, fluorine, hydroxylamine, iodine monochloride, lead dioxide, nitric acid, nitrous acid, organic matter, potassium, and sodium. A few positives about it are that it will not burn, only decompose and it is a strong reducing agent. 



Uses
For such a toxic chemical, phosphorus trichloride is surprisingly useful. It is mainly used as an ingredient in pesticides, which kills fungi or pests. It is also used as herbicides, which is used to kill weeds. In fact, 90% of phosphorus trichloride production is sold to the company that produces RoundUp. It is the starting product for many inorganic and organic compounds including; phosphorus oxychloride, phosphorus sulfochloride, phosphorus acid, alkyl phosphites, and dialkyl phosphites. Phosphorus trichloride can also be used as a stabilizer for plastic, a chlorinating agent in organic synthesis,an ingredient in water treatment chemicals, or a paint additive. Because of its inflammability, it is used as a flame retardant to plastics. It also serves as a catalyst for the production of fatty acid chlorides. 

Nerve Agents
Nerve agents are toxic gases that are inhaled or absorbed through the skin and have harmful effects on the nervous and respiratory system. All of them are colorless liquids in their base state. Since all the nerve agents belong to the organo-phosphorus compounds, phosphorus trichloride is considered to be a nerve agent. This is because the phosphorus bond is considerably weaker when compared to other bonds, and are easily broken. Nerve agents get their name because they block the signal from the nerves to the brain. Their effects rapidly spread through the skin, as well as the respiratory system, where the poisoning spreads much quicker.

The first nerve agent was discovered in 1934 by German chemist Dr. Gerhard Schrader. The toxic chemical was named tabun and the Nazi party later produced 12000 tons of it during World War 2. They also created two additional nerve agents, giving the trio the name "G agents". After the war, the Allies took most of the tabun and studied it in order to learn better methods of protection. In the process, they discovered what became known as the "V agents", which were ten times more poisonous than the G agents. Surprisingly, a few were available as pesticides, but were quickly taken off the public market for obvious reasons. Since creating nerve agents is a fairly simple chemical technique, and the materials are inexpensive, nerve agents are often a weapon of evil rather than a tool for good.