posted February 02, 2000 07:40 AM            

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EASY NERVE GAS (DFP)

DFP is the easiest true nerve agent that can be made at home. By easy, don't get the idea that I mean you can whip up a batch in a bucket. You can't. But compared to Sarin or VX it's quite easy.

Technical Details

Synonyms: DFP, diisopropyl phosphorofluoridate, Dyflos, isopropyl fluophosphate.

Military Symbol ?; CAS Registry # 55-91-4; Merck Index Reference #5029, pg 678. (9th ed.)

Formula Weight 184.15; Specific Gravity (Density) 1.055 (H 2 O = 1); Melting/ Boiling Points MP -82° C / BP 183° C (decomposes), 62° C / 9mm; Vapor Density 6.3 (air = 1.0); Vapor Pressure 0.579mmHg at 20° C; Appearance Clear, practically odorless, mobile liquid

Solubility H 2 O (25° C) 1.54% w/ w (dec.; pH ~ 2.5). Soluble in vegetable oils; not very soluble in mineral oils.

Preparation

180 grams (3 mols) of anhydrous isopropyl alcohol is dissolved in 100 milliliters of carbon tetrachloride (CCl 4 ), and 137.5 grams (1 mol.) of phosphorus trichloride (PCl 3 ) is added slowly without external cooling in a 1 liter flask.

It's necessary for the mixture to warm to about 50 - 60° C in order for the reaction to proceed at a reasonable speed.

When the PCl 3 addition is complete, the mixture is kept under reduced pressure with a stream of dry air passing through it for 1 hour. The product is then chlorinated at 0° C by a moderate stream of chlorine gas, until a permanent green color is obtained (about 2 hours).

The liquid is then treated with a stream of dry air under reduced pressure to remove excess chlorine and hydrogen chloride. This usually takes about 3 hours, although the period can often be substantially reduced. (It is essential, however, to remove as much hydrogen chloride (HCl) as possible before fluorination.)

The fluorination is carried out by adding more carbon tetrachloride (about 40 milliliters) to replace that lost by evaporation, and then adding 94.5 grams (2.25 mols) of dry, finely powdered sodium fluoride (NaF) . The mixture is then mechanically stirred and then warmed.

After the initial fairly vigorous reaction subsides, the mixture is gently refluxed for 3 hours, during which time no fuming (indicating moisture or HCl) should have occurred. The product is cooled, filtered, and the carbon tetrachloride distilled off under reduced pressure, and the residual liquid distilled.

A very small fraction is collected at 70 - 75° C / 21mm, followed by the main fraction (138 grams, 75% based on phosphorus trichloride) at 78 - 84.5° C / 21mm of very nearly pure diisopropyl fluorophosphonate. This main fraction distilled almost entirely at 82 - 83° C / 21mm giving the pure compound.

When done preparing the DFP, decontaminate the glassware. 2% aqueous sodium hydroxide (lye( NaOH)) should be kept in readiness in the hood. The flask and other contaminated equipment should be immersed into the solutions and allowed to stand several days. It is important to know that decontamination by cold dilute alkali is effective only when accompanied by vigorous agitation. This point should be kept in mind when dealing with apparatus contaminated by DFP.

When working with DFP, amounts chemically undetectable can cause miosis, even when protective measures are taken. Minute traces of the vapour adhering to clothing can produce significant miosis.

Useage

DFPs main use would be as a lethal inhalant similar to phosgene or hydrogen cyanide. While it is capable of being absorbed through the skin, the amount needed and the length of time for effect rules out its intentional use as such, except for assassinations.

DFP would ideally be atomized by compressed air into a fine mist to be inhaled by the targets. It can also be atomized by explosives. Placing a bottle of DFP close to a pipe bomb so it will be shattered in the explosion would be a very effective way of increasing the killing power of both. Not only would you kill the immediate target with shrapnel, but then anyone responding to the explosion would be lethally exposed to this invisible, odorless nerve gas.

Police, firefighters, paramedics, and bystanders could all fall prey to this "higher form of killing". As an added bonus, future bombing victims would be more likely to die since responding help would be leery of another nerve gas attack. It could also be used to poison bullets, sprayed on victims covertly to kill them, or tiny amounts could be injected into an area to temporarily blind a group of people as a harassment technique.

Experiments show that the L. C. 50 (Toxicity by inhalation (L. C. 50) is expressed as the concentration in milligram/ liter required to kill 50% of the targets exposed) for DFP for 10 minute exposures (deaths within 2 hours) was 0.44 milligram/ liter for mice and 0.36 milligram/ liter for rats. So, on average, 0.4 ounces per 1,000 cubic feet would be fatal on 10 minutes exposure.

A concentration of DFP of 1 part in 10,000 parts in the air killed 18/ 23 of the animals exposed for 10 minutes, all the deaths taking place within 25 minutes of the beginning of the exposure.

This means that the compound is more toxic than phosgene, cyanogen chloride, or chloropicrin. For exposures of less than about 13 minutes the compound is slightly less toxic, and for exposures longer than 13 minutes, more toxic than hydrogen cyanide. The symptoms were salivation, muscular weakness, gasping, and finally cessation of breathing.

The compound is very volatile, has the quick "knock- out" action comparable to that produced by hydrogen cyanide, and resembles hydrogen cyanide and parathion in toxicity.

Pure DFP is a stable chemical that can be stored in sealed containers for years without change but it may develop pressure, therefore it should be stored in a refrigerator or cool place out of sunlight.

Below is a table showing the melting point for various mixtures of mustard gas with DFP. This would be useful as a dual-effect weapon, mustard gas as a vesicant and DFP as a nerve gas. Plus, the DFP allows mustard to be sprayed as a liquid at temperatures that it would otherwise be a solid at.

(Table Deleted)

Decontamination

For disposal, add to a large excess of 2% sodium hydroxide solution. Let stand (with occasional stirring) at least 48 hours to ensure complete hydrolysis (pH should be above 9). Neutralize and flush solution with copious amounts of water.

Medical Aspects

DFP is a powerful inhibitor of cholinesterase, and possesses powerful myotic action (constriction of the pupils of the eyes). DFP is highly toxic by all routes of administration.

Miotic effect

DFP was tested on persons who entered a 10 cubic meter chamber containing a concentration of 1 in 1,000,000 (i. e., 0.0082 milligram/ liter) for 5 minutes. Practically nothing was observed until some 5 minutes after leaving the chamber; severe miosis then set in. This often persisted for as long as 7 days, and there was usually no sign of relaxation until after 72 hours.

The eye effects may be summarized as follows : Pupil constriction. All subjects affected. The amount of light entering the eye was greatly reduced, and darkness set in. The incapacitation was worse in poor light (e. g., at twilight). A. Visual acuity affected. Varied from individual to individual. B. Powers of accommodation affected. The younger subjects usually suffered most. C. Photophobia and headaches almost always accompanied the miosis. Pain was experienced when changing from a bright to a dull light. D. Congestive iritis was caused by rather higher concentrations than the above, e. g., at 0.05 milligram/ liter for 5 minutes.

Symptoms

Mild - headache, anorexia, nausea, weakness, dizziness, blurred vision and myosis.

Moderate - vomiting, abdominal cramps, diarrhea, salivation, lachrymation, sweating, dyspnea, substernal tightness, slow pulse, tremors of extremities, muscular cramps and ataxia.

Severe - fever, cyanosis, pulmonary edema, areflexia, loss of sphincter control, convulsions, coma, heart block, shock and respiratory failure.