CS-GAS
The compound 2-chlorobenzalmalononitrile (also called o-chlorobenzylidene malononitrile) (chemical formula: C10H5ClN2), a cyanocarbon, is the defining component of a tear gas commonly referred to as CS gas, which is used as a riot control agent. CS gas is an aerosol of a volatile solvent (a substance that dissolves other active substances and that easily evaporates) and 2-chlorobenzalmalononitrile, which is a solid compound at room temperature. CS gas is generally accepted as being non-lethal. It was discovered by two Americans, Ben Corson and Roger Stoughton, at Middlebury College in 1928, and the chemical's name is derived from the first letters of the scientists' surnames.
CS was developed and tested secretly at Porton Down in Wiltshire, England, in the 1950s and 1960s. CS was used first on animals, then subsequently on British Army servicemen volunteers. CS has less effect on animals due to "under-developed tear-ducts and protection by fur".
Production
CS is synthesized by the reaction of 2-chlorobenzaldehyde and malononitrile via the Knoevenagel condensation: CS-chemical-synthesis
ClC6H4CHO + H2C(CN)2 → ClC6H4CHC(CN)2 + H2O
The reaction is catalysed with weak base like piperidine or pyridine. The production method has not changed since the substance was discovered by Corson and Stoughton.[7] Other bases, solvent free methods and microwave promotion have been suggested to improve the production of the substance.
The physiological properties had been discovered already by the chemists first synthesising the compound in 1928: "Physiological Properties. Certain of these dinitriles have the effect of sneeze and tear gases. They are harmless when wet but to handle the dry powder is disastrous."
Use as an aerosol
As 2-chlorobenzalmalononitrile is a solid at room temperature, not a gas, a variety of techniques have been used to make this solid usable as an aerosol:
Melted and sprayed in the molten form.
Dissolved in organic solvent.
CS2 dry powder (CS2 is a siliconized, micro-pulverized form of CS).
CS from thermal grenades by generation of hot gases.
In the Waco Siege, CS was dissolved in the organic solvent dichloromethane (also known as methylene chloride). The solution was dispersed as an aerosol via explosive force and when the highly volatile dichloromethane evaporated, CS crystals precipitated and formed a fine dispersion in the air.
Effects
CS Gas used at May Day 2013, Istanbul
Tear gas shells used in Istanbul in 2013
CS gas shells used in Taksim Gezi Park, Istanbul, May 2013
Many types of tear gas and other riot control agents have been produced with effects ranging from mild tearing of the eyes to immediate vomiting and prostration. CN and CS are the most widely used and known, but around 15 different types of tear gas have been developed worldwide e.g., adamsite or bromoacetone, CNB, and CNC. CS has become the most popular due to its strong effect and lack of toxicity in comparison with other similar chemical agents. The effect of CS on a person will depend on whether it is packaged as a solution or used as an aerosol. The size of solution droplets and the size of the CS particulates after evaporation are factors determining its effect on the human body.[9]
The chemical reacts with moisture on the skin and in the eyes, causing a burning sensation and the immediate forceful and uncontrollable shutting of the eyes. Effects usually include tears streaming from the eyes, profuse coughing, exceptional nasal discharge that is full of mucus, burning in the eyes, eyelids, nose and throat areas, disorientation, dizziness and restricted breathing. It will also burn the skin where sweaty and/or sunburned. In highly concentrated doses it can also induce severe coughing and vomiting. Almost all of the immediate effects wear off within an hour (such as exceptional nasal discharge and profuse coughing), although the feeling of burning and highly irritated skin may persist for hours. Affected clothing will need to be washed several times or thrown away.
Secondary effects
People or objects contaminated with CS gas can cause secondary exposure to others, including healthcare professionals and police. In addition, repeated exposure may cause sensitisation.
Toxicity
Although described as a non-lethal weapon for crowd control, many studies have raised doubts about this classification. As well as creating severe pulmonary damage, CS can also significantly damage the heart and liver.
On 28 September 2000, Prof. Dr. Uwe Heinrich released a study commissioned by John C. Danforth, of the United States Office of Special Counsel, to investigate the use of CS by the FBI at the Branch Davidians' Mount Carmel compound. He concluded that the lethality of CS used would have been determined mainly by two factors: whether gas masks were used and whether the occupants were trapped in a room. He suggests that if no gas masks were used and the occupants were trapped, then, "...there is a distinct possibility that this kind of CS exposure can significantly contribute to or even cause lethal effects."
Many reports have associated CS exposure with miscarriages. This is consistent with its reported clastogenic effect (abnormal chromosome change) on mammalian cells.
When CS is metabolised, cyanide can be detected in human tissue.According to the United States Army Center for Health Promotion and Preventive Medicine, CS emits "very toxic fumes" when heated to decomposition, and at specified concentrations CS gas is an immediate danger to life and health. They also state that those exposed to CS gas should seek medical attention immediately.[2]
In Israel, CS gas was reported to be the cause of death of Jawaher Abu Rahmah on 31 December 2010, although the Israel Defense Forces have questioned the veracity of the report. In Egypt, CS gas was reported to be the cause of death of several protesters in Mohamed Mahmoud Street near Tahrir square during the November 2011 protests.
The solvent in which CS is dissolved, methyl isobutyl ketone (MIBK), is classified as harmful by inhalation; irritating to the eyes and respiratory system; and repeated exposure may cause skin dryness or cracking.
Use
RWGŁ-3 Polish tear gas grenade launcher.
CS was used to flush the Viet Cong from their tunnels in the Vietnam.
CS is used in spray form by many police forces as a temporary incapacitant and to subdue attackers or persons who are violently aggressive. Officers who are trained in the use and application of CS spray are routinely exposed to it as part of their training.
Blank pistol cartridges carrying CS in powder form have been released to the public. These, when fired at relatively close ranges, fully expose the target to the effects of CS, and are employed as a potent defensive weapon in regions where blank firing pistols are legally permitted for such use.[citation needed]
Although predominantly used by police it has also been used in criminal attacks in various countries.[15][16][17][18]
Use of CS in war is prohibited under the terms of the Chemical Weapons Convention, signed by most nations in 1993 with all but five other nations signing between 1994 and 1997. The reasoning behind the prohibition is pragmatic: use of CS by one combatant could easily trigger retaliation with much more toxic chemical weapons such as nerve agents. Only five nations have not signed the Chemical Weapons Convention and are therefore unhindered by restrictions on the use of CS gas: Angola, Egypt, North Korea, Somalia, and Syria.
Domestic police use of CS is legal in many countries, as the Chemical Weapons Convention prohibits only military use.
