Alternative Technologies for the Destruction of Chemical Agents and Munitions (1993)
Chapter: DESCRIPTION OF THE AGENTS
2
The U.S. Chemical Weapons Stockpile
This chapter presents a brief description of the U.S. chemical weapons stockpile, covering the physical properties of chemical agents, their toxicities, associated weapons, and the nature and distribution of stockpile storage sites.
DESCRIPTION OF THE AGENTS
The U.S. chemical weapons stockpile contains nerve agents, or nerve gas, and blister, or mustard, agents. (Mustard was used extensively in World War I, whereas nerve agents were first used in war by Iraq in its war with Iran.) These two fundamental types of chemical warfare agents are contained in the U.S. stockpile in a variety of munitions and bulk containers.
Nerve agents in the U.S. stockpile include persistent VX, nonpersistent Sarin (GB), and a small quantity of Tabun (GA). All the nerve agents are organophosphonate compounds, which contain phosphorus double-bonded to an oxygen atom and single-bonded to a carbon atom. VX also contains sulfur in its chemical structure, GB contains fluorine, and GA contains the cyanide group (see Figure 2-1 for the chemical structures of major U.S. chemical agents and Table 2-1 for some of their physical properties).1
Nerve agents are highly toxic or lethal in both liquid and vapor forms.2 Although they are often referred to as gases, they are liquids at normal
FIGURE 2-1 Principal chemical wadare agents in the U.S. stockpile.
temperatures and pressures. GB has a boiling point about 5°C lower than that for kerosene or diesel fuel. It evaporates at about the same rate as water and is relatively nonpersistent in the environment. VX evaporates much more slowly, and spills of liquid VX can persist for a long time under average weather conditions. Thus, GB presents mainly a vapor hazard, although contact with its liquid form can also be fatal. In contrast, VX presents mainly a contact hazard, although its vapor buildup in enclosed spaces can also reach lethal levels. In their pure form, all these nerve agents are nearly odorless and colorless.
The blister agents include H, HD, and HT. The active ingredient in H and lid and a major component (60 percent) of HT is the same chemical substance, bis(2-chloroethyl)sulfide, or mustard.3 The agent H, sometimes called Levinstein mustard, contains 70 percent mustard and 30 percent
TABLE 2-1 Physical Properties of Chemical Warfare Agents
Agent Characteristic | Nerve Agents | Blister (Mustard) Agents | ||
GB (Sarin) | VX | H/HD | HT | |
Chemical formula | (CH3)2CHO(CH3)FPO | C11 H26NO2PS | (ClCH2CH2)2S | 60% (ClCH2CH2)2S, 40% sulfur and chlorine compounds |
Molecular weight | 140.10 | 267.38 | 159.08 | Not available |
Boiling point, °C | 158 | 298 | 217 | 228 |
Freezing point, °C | -56 | < -51 | 14.45 | 0 to 1.3 |
Vapor pressure, mm Hg | 2.9 @ 25°C | 0.0007 @ 25°C | 0.072@ 20°C | Not available |
Volatility, mg/m3 | 4,100@ 0°C 22,000@ 25°C | 10.5 @ 25°C | 75 @ 0°C (solid) 610 @ 20°C (liquid) | 831 @ 25°C |
Diffusion coefficient for vapor in air, cm2/sec | 0.061@ 20°C | 4 @ 20°C | 0.060@ 20°C | 0.05@ 25°C |
Surface tension, dynes/cm | 26.5@ 20°C | 32.0@ 20°C | 43.2@ 20°C | 44 @ 25°C |
Viscosity, cS | 1.28@ 25°C | 12.256@ 20°C | 3.95 @ 20°C | 6.05@ 20°C |
Agent Characteristic | Nerve Agents | Blister (Mustard) Agents | ||
GB (Sarin) | VX | H/HD | HT | |
Liquid density, g/cm3 at 20°C | 1.0887 | 1.0083 | 1.2685 | Not available |
Latent heat of vaporization, cal/g | 80 | 78.2 | 94 | Not available |
Solubility, g/100 g of distilled water | 100; soluble in organic solvents | 5 @ 25°C; best solvents are dilute mineral acids | 0.92 @ 22°C; soluble in acetone, CCl4, CH3Cl, tetrachloroethane, ethyl benzoate, ether |
|
Heat of combustion, Btu/lb (cal/g) | 10,000 (5.55) | 15,000 (8.33) | 8,100 (4.5) | Not available |
Source: Chemical Systems Laboratory (1983); Programmatic Environmental Impact Statement (PEIS) (1988). U.S. Departments of the Army and Air Force (1975). | ||||
