WP: white phosphorus; one of several allotropes of
elementalphosphorus.
Elemental: uncombined with other elements.
White phosphorus combines spontaneously with atmospheric oxygen, self-heating to the ignition temperature, at which time rapid combustion takes place, combustion temperature exceeds 2000 C, forming phosphorus pentoxide, m.p. 563 C, sublimes at 347 C, no pressure specified (in dry air).
Metaphosphoric acid, HPO
3, forms on solution of P
2O
5 in water, and also forms on heating orthophosphoric acid [H
3PO
4 to 316 C. Metaphosphoric acid reacts slowly with additional water at temperatures less than 213 C to form orthophosphoric acid. There is a third hydrated form, pyrophosphoric acid, H
4P
2O
7 observed between 213 and 316 C when heating orthophosphoric acid. Metaphosphoric acid will coagulate egg white, and it is reasonable to extrapolate this property to other proteins. The ortho- and pyro- acids do not exhibit such activity.
Selected heats of combustion and reaction with water (per kg(P)): formation of P
2O
5, 24.7 MJ/kg(P); formation of metaphosphoric acid, HPO
3, 30.1 MJ/kg(P).
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Estimation of tissue properties
vis a vis charring, "melting the skin," psychological or morale effects.
Sp. ht. ~ 4kJ/kgK; the body is 70% water, and the remaining bioorganics do not have a significantly different sp. ht..
Charring temperature? Shall we take Bradbury's book? 451 F is equivalent to 233 C, 506 K. Body temperature is 37 C, or 310 K. Enthalpy of vaporization of water is 2.4 MJ/kg. Mass of the human skin and affected near surface tissues is going to be taken as 15 kg.
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We are now prepared to do the energy balance on the "atrocity." The energy will be cacluated as the sum of the energies to raise 1 kg tissue to the b.p. of water, the energy required to evaporate 70% of the mass as water, and the energy required to raise the dry residue to 500 K. From 310 K to 373 K, ΔT = 60 K (I'll be rounding in favor of the "Nuremburg tribunal), and the heat per kg is 0.24 MJ. Evaporating 0.7 kg water takes another 1.68 MJ. Raising the remaining 0.3 kg from 370 to 500 K requires another 0.2 MJ. Total heat necessary to char tissue is 2.1 MJ/kg.
Heat available from production of metaphosphoric acid from 1 kg P is 30.1 MJ/kg; dividing by char heat, 30.1/2.1 = 14.3 kg(charred tissue)/kg(P).
We'll take burns over 20% of the body as having a 50% mortality rate, and cut that in half given the "chemical" complications that can arise. Now we can kill 70 people with a single kg(P) if we get perfect partitioning from our delivery system.
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Delivery systems: we've got the 120 mm mortar, and the 155 mm howitzer, and a couple different WP rounds for each. Didn't find actual filler capacities for either, too much Fallujah spam to sort through, so we'll pack 'em the way college kids used to pack VWs and phone booths --- call it 10 kg/mortar and 30 kg/howitzer round.
Bursting charges may or may not be designed to mimic casualty radii of VT fused fragmentation bursts --- it would drive gunners and observers nuts if they weren't, since the most common use is as a "marker round" for adjusting fire. 120 mm has got a casualty radius of probably 30 - 40 m, and we'll call it 25 m. The 155 we'll call 50 m (105 mm from the Nam era was good for a football field). Our phosphorus delivery rates for the two systems are then 10 kg/(π x 625 m
2) and 30 kg/(π x 2500 m
2), 5 g/m
2 for the mortar, and 4 g/
2 for the howitzer.
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Our victims then have to have been within 25 or 50 meters of 20 - 25 mortar or howitzer impacts or airbursts, given that we give them a 1 m
2 cross section. No one holds still in the vicinity of a target drawing that sort of attention. Shoot up the whole area? Okay, takes an impact density of 0.01 mortar round/m
2, or 0.003 howitzer round/m
2 to get the phosphorus delivery rate up to what's required (100 g/m
2). Three to ten thousand rounds per square kilometer, and the Fallujah map
http://www.globalsecurity.org/military/world/iraq/fallujah-imagery-forces.htm covers something like 10 km
2 if we take the "contested area" as being encompassed by the marked start lines and the E-W highway. Hundred thousand WP mortar rounds? Thirty thousand 155 mm WPs?
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Aerosol effects: Just how toxic is the smoke cloud. Mass of air into which the two systems burst is, again we'll cater to the tribunal and use small radii estimates, (4/3)π15625 m
3 x 1 kg/m
3, 65,000 kg for the mortar round, and 500,000 for the howitzer. We'll cut these in half for ground bursts. One kg(P) will yield 2.3 kg(P
2O
5, or 2.6 kg(HPO
3). The metaphosphoric acid is the heavier, and average mass concentrations are 800 ppm for mortar, and 300 ppm for howitzer ground bursts.
How dangerous is this concentration? I haven't got Sax or Patty's at hand. http://www.omega23.com/Professional_zone/Industrial_Hygiene_and_Toxicology.html
http://books.mysic.ca/0442004974++Hazardous+Chemicals+Desk+Reference
For anyone who wants to hunt 8 hr. threshholds.
The "knockdown" (respiratory arrest so pronounced that the victim suffocates --- without actually inhaling any of the gas into the lungs) concentration for H
2S is 500 - 1000 ppm depending upon individuals and exposure histories. Exposure times at 50 -100 ppm should be limited to minutes. Time to severe, splitting, top of my head's coming off headache at ppm levels vary from 10 min. to all day long. Olfactory threshold varies from parts per trillion to 10s of parts per billion. Hydrogen sulfide is more toxic than hydrogen cyanide, but considered less hazardous because of the low detection threshhold.
Is phosphorus pentoxide or phosphoric acid in the same category of toxicity as cyanide or hydrogen sulfide? Not by several orders of magnitude.
"Corrosive" (or other reactive) effects: The metaphosphoric acid denaturization of protein is probably the biggest hazard. Every one who has struck a kitchen match and had the wind shift to blow the fumes into the face, nose, and eyes has experienced a pretty good approximation of what a WP smoke cloud is going to do. Clouded vision, the eyes are rather amazing at sluffing damaged cells from the sclera, that clears quickly, runny nose, pulmonary edema, coughs out in a day or two, unless you're a smoker and snorting kitchen matches several times a day.
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Tactical Doctrine: WP is used as a marker round (adjusting fire, and in the days of the Nam, pre-GPS, navigation), an incendiary for igniting fires in flammable stores, for screening (hiding our movements from the bad guys), or blocking (putting the bad guys in the fog). Sometimes the mention is made that it's NOT an anti-personnel weapon, sometimes it's left as an exercise to the tactics student to realize that it's
useless as an anti-personnel weapon; a disciplined force is going to ignore it as no more than a nuisance to visibility, which is what it is. The odd burns requiring specific treatment are no more severe than what occurs changing barrels on M60s barehanded, accidental ignition of smoke grenades in cargo pockets of clothing, but do serve to p*ss them off to the point that you'll wish you had some real anti-personnel weapons.
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International Law: the cold war begat the nuclear arms race, begat MAD, begat fear of Armageddon, begat
straightforward diplomacy regarding strategic policies, begat exchanges of specific information regarding conditions under which first use of nuclear weapons was part of war plans, begat disclosure of NATO and Warsaw Pact policies that use of chemical or biological weapons would be regarded as grounds for first use, begat treaties, conventions, and resolutions outlawing chemical and biological weapons.
That's the easy part --- chemical weapons were useless in WW I, and no one since has come up with any means of employing the damned things that is reliable enough to justify maintaining chemical capabilities. The wind shifts and you're done. So everyone smiles, signs the treaty, and starts thinking about where to spend the money that used to go toward maintaining a useless capability.
Now, for the hard part: WW II introduced the world to "modern total war," unconditional surrender, logistical targets being extended to include the "economic base" (civilian population) supporting belligerent forces, and just plain gratuitous malice. If we can ditch useless weapons, can we ditch the idea of direct attacks on "economic bases?" Put 'em out of the arms busines, or taxpaying, but let's not deliberately target civilians or non-combatants. Added benefit being, if economies are not totally destroyed, post-conflict recoveries are facilitated.
What's this got to do with WP? Good intentions outran reality. Incendiaries work. Weapons that work remain in service. Is it nasty stuff? Yeah. Can the burns cause serious problems if not treated properly? Yeah. Can it melt people? Only if you break open a round and "butter" them like an ear of corn with the stuff.