Sarin evaporation

Tokyo, Japan on March 20, 1995, where hve trains would meet at 8 15 am. Members of the sect on the trains pierced plastic bags containing 30% Sarin with sharp tipped umbrellas and let the Sarin evaporate into a lethal gas cloud. Twelve passengers on the train died and about 5500 sought medical treatment (Biema, 1995 Ohbu and Yamashina, 1997). 

Immediate decontamination is required for the smallest drop. VX can be very rapid, and death can occur within fifteen minutes after absorption of a fatal dosage. Heavily splashed liquid persists for long periods under average weather conditions, and VX can persist for months in cold weather. For instance, VX is calculated to be approximately 1,500 times slower in evaporation than sarin (GB). As for LD-50 dose on the skin, sarin (GB) requires a dose of 1700 mg while VX requires only ten mg (tabun requires 1000 mg, soman requires 50 mg, and GF requires 30 mg). 

In Japan, a number of years ago, a terrorist attack with sarin killed a dozen individuals confined to a subway car out of roughly a thousand people in the nearby vicinity. Sarin has little effect on the skin, due to rapid evaporation. It is true that the Iraqis killed many Kurds with nerve gas, but the victims were unprepared, had no training, no detection devices, no masks or other protection, no antidote and no practical way to avoid the gas. None of these vulnerabilities would be the case in a conflict with American troops. 

Remove the reflux head, hook up a vacuum Hource with solvent trap and evaporate the solvent under reduced pressure. Warning - The product is now crude Sarin and must be handled accordingly. 

The USA adopted sarin as its nerve agent after the war and then developed a more sophisticated gas, VX. This is not volatile and is described as persistent, remaining in a sprayed area, whereas sarin is non-persistent, that is, it evaporates and therefore a sprayed area becomes less hazardous with time. 

The G agents present a vapor hazard as they are very volatile. VX has a high dermal toxicity, even through intact skin, as the liquid does not evaporate quickly (Berkenstadt et al, 1991 Sidell et al, 1997). VX is 300 times more toxic than tabun on skin. A very small drop on the skin may cause sweating and fasciculations at the site. A larger dermal drop may cause loss of consciousness, seizures, apnea, and flaccid paralysis. Toxicity in descending order, on a per weight basis, is VX > soman > sarin > tabun (HSDB, 2008). 

The G agents are volatile and evaporate over several hours. They are nonpersistent in the environment (Garigan, 1996). Environmental persistence is estimated to be 0.5 to 1 day for tabun, 1 to 2 days for soman, and 5 days for sarin. VX is an oily liquid that remains in the environment for weeks or longer after being dispersed (Budavari, 2000 Garigan, 1996 Munro et al, 1999 Sidell et al, 1997). Contaminated soil should be treated with alkaline substances (sodium carbonate, sodium bicarbonate, calcium hydroxide, calcium hydroxide, or calcium carbonate) or chlorine compounds (sodium hypochlorite or calcium hypochlorite) (EPA, 1975). 

Nerve agents are absorbed both through the skin and via respiration. Because VX is an oily, nonvolatile liquid it is well absorbed through the skin (persistent nerve agent), although it can also be absorbed by inhalation. Thus, VX is more of a percutaneous threat than by inhalation, whereas the G agents (nonpersistent), which are also liquids, pose more of an inhalation hazard because of their vapor pressure. Sarin (GB) is the most volatile, but evaporates less readily than water, while cyclosarin (GF) is the least volatile of the G agents. 

The interaction of environmental surface and temperature influences the persistence of a liquid biological and chemical threat agent. As with other liquids, evaporation increases as the temperature rises. Sarin is reported to evaporate in half the time at 43°C compared to a temperature of 10°C from a sandy soil (Sidell et al. 1998). For evaporation of sarin from a chemical-resistant surface, the times are 2 min. and 15 min., respectively (Sidell et al. 1998). 

The nerve agents are liquid under temperate conditions. When dispersed, the more volatile ones (G Agents), constitute both a vapor and liquid hazard. Sarin (GB) is the most volatile, although it evaporates less readily than water. Of the G agents, GA is the least volatile. The much less volatile V agents (such as VX) represent primarily a liquid hazard. 

Vlt Volatility of the agent. Volatility is a measure of how much agent will evaporate under a given set of environmental conditions. The volatility of an agent can be compared to a hazardous exposure level to determine the potential risks. For example, the volatility of sarin is 2,800 ppm the LC50 for a 10-minute exposure is 1.2 ppm. The concentration produced by evaporating sarin is over 1,000 times this lethal level. 

The toxicity of liquid nerve agents on the skin was studied extensively. In the first study reported (Freeman et al, 1953), 5-mg droplets of sarin (6-129 droplets total doses of 25-550 mg) were placed on the volar aspects of the forearms of 11 subjects. The agent evaporated in 1.5-6 min from the skin when the area was relatively free of hair, and in 6.5-15 min from the skin when placed in areas of heavy hair. The agent was mixed with a dye for visualization, and after evaporation was complete the site was tested for the agent and then decontaminated. Maximal inhibition of erythrocyte cholinesterase activity was 18% (82% of normal). Two subjects (cholinesterase of 82%) had transient diarrhea. Sweating at the site of application continued for as long as 34 days. 

A small amount (3.21 mg) of liquid sarin was applied to the skin of six subjects, and about 98% of it was recovered in the air (Marzulli and Williams, 1953). The tendency of sarin to evaporate rather than to penetrate skin was noted in a later, more extensive study (MOD6). In a similar study by two of the same investigators (Freeman et al, 1954), tabun, 50-400 mg in 0.5-mg droplets was placed on the volar aspects of... 

Is the nerve agent a volatile or non-volatile liquid Sarin (volatility = 21 862 mg m-3 at 25°C) is much more volatile than tabun (611 mg m 3 at 25°C), although both agents tend to evaporate from the skin (or other surface) more quickly than VX, which is a non-volatile oily liquid (10.07 mg m-3 at 25°C) (Maynard and Beswick, 1992). 

This is a measure of how quickly a nerve agent will evaporate and is increased by a rise in ambient temperature. For example, the vapour pressure for sarin is 0.52 mmHg at 0°C and 2.9 mmHg at 25°C (Maynard and Beswick, 1992), whereas that of tabun is 0.004 mmHg at 0°C and 0.07 mmHg at 25°C (Maynard and Beswick, 1992). 

On 20 March 1995, a terrorist attack occurred in the Tokyo subway system during rush hour. Sarin was placed in five subway cars on three separate lines in plastic bags opened so that the agent, which is liquid under temperate conditions, could evaporate. Over 5000 casualties sought medical attention of whom 984 were moderately poisoned and 54 were severely poisoned 12 died. However, a substantial number of those... 

Compared with other nei ve agents, soman is more volatile than VX but les,s volatile than sarin. The higher a chemical s volatility, the more likely it will evaporate from a liquid into a vapor and disperse into the environment. People can be exposed to the vapor even if they do not come in contact with the liquid form. 

Sarin is a clear, colorless, and tasteless liquid that has no odor in its pure form. However, sarin can evaporate into a vapor (gas) and spread into the environment. 

Becau.se it evaporates so quickly, sarin presents an immediate but short-lived threat. 

Chemicals such as mustard (a blister agent) and sarin (a nerve agent) can form toxic vapors at room temperature. Agents that share this physical property could be employed in crude but still very deadly attacks without sophisticated dispersal devices. Other, more viscous compounds such as VX are much less prone to evaporation even at higher temperatures, and for this reason present more of a hazard as a skin contaminant. 

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