Chemical agents volatility

Decontamination. If contaminated equipment or material does not have to be used immediately, natural aeration is an effective decontaminant procedure, as most chemical agents, including the bHster and V-agents, are volatile to a certain degree. Wind accelerates their evaporation and hastens their dissipation. Rain and dew may also cause sufficient hydrolysis of some agents. Sunlight increases the surface temperatures of military equipment and thus accelerates agent evaporation. 

Vapor pressure Volatility 11,100 mmHg at 20°C. This high vapor pressure means that SA is difficult to liquefy and to store. 30,900,000 mg-min/m3 at 20°C. This by far the highest volatility found among the compounds considered for tactical use as chemical agents. This fact, coupled with a relatively low latent heat of vaporization, qualifies SA as the most rapidly dispersing chemical agent. 

Substances with high vapor pressure evaporate rapidly. Those with low vapor pressure evaporate slowly. The impact of vapor pressure on the rate of evaporation makes vapor pressure a very important property in considering the tactical use and duration of effectiveness of chemical agents. A potential chemical agent is valuable for employment when it has a reasonable vapor pressure. One with exceptionally high vapor pressure is of limited use. It vaporizes and dissipates too quickly. Examples are arsine and carbon monoxide. On the other hand, mechanical or thermal means may effectively aerosolize and disseminate solid and liquid agents of very low vapor pressure. Vapor pressure and volatility are related. Translated into volatility, vapor pressure is most understandable and useful. 

Decontamination Decontaminate eyes and skin. Even though this chemical agent is highly volatile, pay particular attention to the eyes. Remove wet, contaminated clothing and the underlying skin decontaminated with water. 

Persistent Agent Chemical agents that do not hydrolyze or volatilize readily, such as VX and HD. At the time of release, this agent can produce casualties for an extended period of time up to several days. Usually, it has a low evaporation rate. Since its vapor is heavier than air, its vapor cloud will hug the ground and accumulate in low areas. It is an inhalation hazard, but extreme care should be taken to avoid skin contact as well. 

The fnndamental differences between chemical and biological agents are very important as we look to the future. Chemical agents are volatile and dermally active and it is immediately apparent when there is hnman contact with a chemical agent. Biological agents, however, are not volatile, not dermally active, and... 

A key parameter used to estimate or model volatilization processes is the pesticide vapour pressure a fundamental property of the chemical agent which is uniquely defined by the temperature. This parameter is readily and reproducibly measured in the laboratory. Two... 

The job of a chemical munition is to create a toxic environment over as much of the target as is compatible with the toxicity of its charge. It must convert its bulk load either into an even distribution of liquid or solid particles, or into a cloud of vapour, or into both. It must, additionally, do this in a certain time. These are strict demands, and they are made more severe by the diversity of chemical agents now in stockpiles. Each agent has a combination of physical characteristics and toxic behaviour that is unique but, nevertheless, all munitions work on the same basic principle they cause the transfer of energy from a store, generally an explosive, to the chemical load. The simplest chemicals to disperse are the volatile, non-persistent ones such as phosgene the hardest ones... 

Risk, D., Verpy, D., Conley, J.D., Jacobson, T., Sawyer, T.W. (2001). Volatile anesthetics give a false-positive reading in chemical agent monitors in the H mode. Mil. Med. 166 708-10. 

FIGURE 53.2. Chemical structures, volatility (at 25°C) and inhalation toxicity data of chemical warfare agents. 

In this formula 8 signifies the persistency of the chemical agent, C the rapidity of volatilization of water at 16 C., c the rapidity of volatilization of the chemical at the absolute temperature T, pi the vapor pressure of water at 15 C., p the vapor pressure of the substance at the temperature T,. V, the molecular weight of the water, M that of the substance, T the ab.Holute temperature of the air, Fi the absolute temperature corresponding to the Celcius tem >erature of 15 . 

In the alwve tabulation all data are based on the rapidity of evaporation of water at 15 C., without making any assumption as to the absolute time of evaporation. Different influences play a weighty role on the length of time that pa.sscs before a chemical agent, placed on a terrain, is iHunpletely volatilized. 

At ordinary temperatures (68 F.), its volatility is only 3.3 mg. i>er liter, which i.< low for a lung injurant but high for a vesicant. Dimethyl sulfate is very readily dccompo.scd by water so that its vapors quickly combine with moisture in the air to form sulfuric acid. ThU is one of the chief d( fect.s of this substance as a chemical agent. 

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