INDC Journal

« | Main | Busy Morning (Revisado) »

November 17, 2005
White Phosphorus: Here Comes The Science

Posted by Dorkafork
(Or "some" science, at least. I am not an expert, and I can't claim this is definitive.)

An argument seems to be going around (for example, in the comments to this post) that WP manages to burn skin without affecting clothing through the following process: burning white phosphorus creates phosphorus pentoxide which reacts with water in the human body to create phosphoric acid, which is "highly corrosive" and burns the skin without burning clothing. Well, let's take a closer look at this.

First of all, let me note that the smoke generated by WP is not harmless. You can tell by reading previous descriptions, it can have harmful effects on your health. And these effects are minor. "Mild irritations" or a "cough".

Now it's one thing to say that white phosphorus (P4) creates phosphorus pentoxide (P4O10 often rendered P2O5) which when combined with water creates phosphoric acid (H3PO4). This part is true, but doesn't really tell you as much as you might think. These chemical reactions can and do take place. But chemistry is more complicated than that. For example, iron reacts with oxygen to form iron oxide (and you can find a list of health effects from Googling, too). What is iron oxide? Fe2O3, also known as rust. Now, does iron, when exposed to oxygen, immediately begin to rust? Well, technically, yes it does. But at what rate? How much rust is formed? That's the important part.

Now let's look at phosphoric acid (H3PO4). "Acid" sounds bad, doesn't it? Well, I'll have you know that I have been drinking phosphoric acid while writing this post. Again, quantity is the key. (It's in Coke and other sodas. Take a look at the ingredients on a Coke. From what I understand, the ingredients are listed in order of amount. That means there's more phosphoric acid than caffeine in a can of Coke.*) Also, although phosphoric acid is an acid, it is considered a weak to "not particularly strong" acid. Another thing we can look at is the acid-dissociation equilibrium constant (Ka). In general, the higher the Ka (acid-dissociation equilibrium constant) value of an acid, the stronger it is. Now lets look at the Ka value of common acids:

Strong Acids     Ka  
***************************************
hydrochloric acid (HCl)   1 x 106  
sulfuric acid (H2SO4)   1 x 103  
hydronium ion (H3O+)   55  
nitric acid (HNO3)   28  
         
Weak Acids     Ka  
***************************************
phosphoric acid (H3PO4)   7.1 x 10-3  
citric acid (C6H7O8)   7.5 x 10-4  
acetic acid (CH3CO2H)   1.8 x 10-5  
boric acid (H3BO3)   7.3 x 10-10  
water (H2O)   1.8 x 10-16  


The Ka value of phosphoric acid is about 4,000 times less than that of nitric acid, the weakest "strong acid" listed. And it's only 10 times greater than citric acid. And we don't know how much phosphoric acid is formed.

All of this I've posted looks impressive, but it is simplified and an expert in chemistry could probably point out mistakes, like how the process of rust formation is simplified. (Naturally I think my logic and sources are sound.) This is part of the point. There are a lot of amateur Google chemists (like me) floating around now that don't necessarily know what they're talking about (like me!). (I'd just like to point out that as of the time of this writing, this dailyKos post has a scientifically incorrect equation for the formation of phosphoric acid. "P2O5 + H20 -> H3PO4" is not a balanced chemical equation. If it was P2O5 + 3H2O -> 2H3PO4 it would be a balanced equation. The number of atoms of each element has to be equal on both sides of the equation for it to be balanced - I believe this is taught in high school chemistry.

As far as I'm concerned, the most important thing to note is the reported effects of WP munitions. It is a common and widely used munition, and the health effects are fairly well known. And as we've seen before, "most of these injuries are mild irritations. No human deaths have been reported from exposure to either white phosphorous or RP smokes." You would think that if WP smoke resulted in phosphoric acid that burned flesh without affecting clothing, that maybe any of the large number of soldiers who have been in WP smoke in either training or combat situations would have noticed that, wouldn't you? Especially if it was to the extent of the photos that have been circulating.

* Phosphoric acid "adds a slightly fruity flavor", according to the book Phosphorus: Chemical Elements That Make Life Possible.

(Related, see the WP User Hall of Shame (not a complete listing). Previous WP coverage here, here, and here, and a followup post here.)

Posted by Dorkafork at November 17, 2005 03:58 AM | TrackBack (1)

Trackback Pings

TrackBack URL for this entry:
http://www.indcjournal.com/cgi-bin/mt/dafrules/tapaz.cgi/2150

Comments

Guys, it is not a matter of phosphorus, or any other weapon. If you don't want this war, then resin-coated bullets are also too much. If you want the war, then don't shy killing. Make up your mind.

Danny
www.SamsonBlinded.org

Posted by: Danny at November 17, 2005 07:58 AM

When the crossbow first came out there was a large out cry against it, kingdoms outlawed it and the church condemned it. Why? Because it worked. The bolt was able to penetrate the conventional armor of the time.

But when was a war ever won by the marquis de queensbury rules?

Posted by: Allium at November 17, 2005 11:34 AM

Heh.

I have been burned by phosphoric acid. It happened in organic chem lab. Someone spilled it around the sink where we rinsed our glassware and, while cleaning my glassware, I got it on the bottom of my forearms. There was no immediate pain, but several minutes later my forearms started to itch. I went to the sink and washed them thoroughly with soapy water, but they continued to itch. Several hours later, I noticed a six inch long, 3 inch wide oval welt that was raised about a quarter of an inch on the bottom of both arms. They looked far more like a rash than they did a burn. They itched like hell for about 3 days then started to heal.

These welts were the only result of the application of a fairly large amount of highly concentrated phosporic acid to my skin. To generate enough phosphoric acid to have an equivalent effect from the simple contact of white phosphorous with the water in skin, you'd have to liberally coat the entire area with white phosphorous. Since the WP will violently oxidize almost immediately, producing a large amount of heat in the process, I posit that the "chemical burns" would be least of the victims problems.

Posted by: Terry at November 19, 2005 01:51 PM

You are a complete idiot. None of your chemistry is coherent. White phosphorus is one of the most deadly substances around. You don't think any white phosphorus will be left in the smoke? Go ahead and inhale that, take a look at what phossy jaw has to offer. The Ka of water is no where near its true value. Also, the Ka also has absolutely nothing to do with how badly a chemical can burn you - equilibrium will shift (to the dissociated side) when this reacts with the proteins or lipids in your body.

Posted by: Jeff Kodine at April 7, 2006 07:30 AM

You are a complete idiot. None of your chemistry is coherent. White phosphorus is one of the most deadly substances around. You don't think any white phosphorus will be left in the smoke?

I never said that.

Go ahead and inhale that, take a look at what phossy jaw has to offer.

Yes, I've read about phossy jaw. It's caused by chronic exposure to WP vapor. "The condition might develop slowly over years..." "...prolonged intake may cause anemia, as well as cachexia and necrosis of bone, involving typically the maxilla and mandible (phossy jaw)." Not exactly the type of exposure that occurred in Fallujah.

I don't know what you're point was with that statement. I wasn't trying to argue that WP was harmless. In fact I specifically stated "First of all, let me note that the smoke generated by WP is not harmless." The bold was in the original. I was specifically trying to argue against the idea that phosphoric acid created by WP smoke would not be likely to burn skin without burning clothing.

The Ka of water is no where near its true value.

You're right, other sources put it at 1x10-14. I must be a total moron not to have double checked the figures I got from the General Chemistry Help section of a Purdue University College of Science Chemical Education site. (They changed over to php from html. Old link is now here.)

For what it's worth, the 86th edition of the CRC Handbook of Chemistry and Physics (2005-2006) puts the pKa of phosphoric acid at 2.16 which gives it a Ka of 6.918x10-3, which is only very slightly weaker than the value I printed above. I'd say my point about the strength of phosphoric acid still stands. Not to mention the fact that every source I've seen on phosphoric acid describes it a moderate to weak acid with health effects that range from "when highly diluted, pure H3PO4 is odorless and nontoxic" all the way to "concentrated solutions are irritating to the skin and mucous membranes." (both quotes from the MacMillan Encyclopedia of Chemistry (1997))

Also, the Ka also has absolutely nothing to do with how badly a chemical can burn you - equilibrium will shift (to the dissociated side) when this reacts with the proteins or lipids in your body.

Well maybe I am a moron. I invite to explain this to me more fully. Because according to this medical site: "The severity of the burn is related to a number of factors, including the pH of the agent, the concentration of the agent, the length of the contact time, the volume of the offending agent, and the physical form of the agent." (emphasis added) I don't understand why you'd say that since Ka is used to calculate pH. Unless I'm missing something. This is my understanding of it.

Acids are proton donors (H+). If you add a strong acid to water, those H+ combine with H2O to form H3O+, which is used to calculate pH (-log[H3O+]) Ka is essentially a measure of how easily an acid gives up H+. A stronger acid gives up more H+ resulting in more H30+ and a lower pH. So how does Ka have "absolutely nothing to do with how badly a chemical can burn you"? It has a direct relationship to pH and is used to calculate pH. What am I missing?


Posted by: dorkafork at April 7, 2006 11:24 PM

Thanks for the special work and information! nokia6630

Posted by: teena at July 23, 2006 06:39 AM

This site is a lot of fun very well designed. nokia6630

Posted by: tracey at July 27, 2006 12:32 AM

Posted by: mae at July 30, 2006 02:41 PM

You guys are the 88424 best, thanks so much for the help.

Posted by: Caty Tota at August 14, 2006 12:55 PM

Posted by: micheal at September 27, 2006 09:16 PM

Posted by: dianne at September 28, 2006 11:10 AM

Posted by: babnik at October 22, 2006 07:58 PM

Posted by: carolee at October 28, 2006 03:40 AM

London-born rapper Sway is to be honoured at the BET Hip-Hop awards in the US...

Posted by: Fernando Mcneil at November 12, 2006 08:45 AM

London-born rapper Sway is to be honoured at the BET Hip-Hop awards in the US...

Posted by: Fernando Mcneil at November 12, 2006 08:46 AM

Record company EMI sign a deal with the estate of crooner Dean Martin to use the singer's likeness...

Posted by: Tristin Grey at November 12, 2006 02:37 PM

The Red Hot Chili Peppers are leading the way at this years MTV Europe music awards with four nominations...

Posted by: Leo Hyde at November 12, 2006 08:20 PM

The Red Hot Chili Peppers are leading the way at this years MTV Europe music awards with four nominations...

Posted by: Leo Hyde at November 12, 2006 08:21 PM

Pop trio Atomic Kitten will reform to play a concert in support of jailed Liverpool football fan Michael Shields...

Posted by: Jamal Marble at November 17, 2006 02:31 AM

Alec Baldwin asks for his voice to be removed from an "unfair" documentary about Arnold Schwarzenegger...

Posted by: Sawyer Hollingsworth at November 17, 2006 07:47 AM

Veteran game show host Bob Barker is stepping down from hosting The Price is Right after 35 years...

Posted by: Francis Slack at November 22, 2006 08:19 AM

361e369328ef Nice site shorturl shorturl

Posted by: shorturl at December 20, 2006 06:27 AM

lqnhczwgp ozeclgfvb pbmty bjzpga kpojd zxtladep yvdimsuw

Posted by: novlfmq gsjhyp at January 11, 2007 02:00 AM


I consider that beside Your site there is future!f

Posted by: Rebekah at March 1, 2007 02:41 PM

Colombia's vice president is "baffled" by Kate Moss's success following cocaine allegations...

Posted by: Shaun Grayson at April 17, 2007 04:49 AM

Colombia's vice president is "baffled" by Kate Moss's success following cocaine allegations...

Posted by: Shaun Grayson at April 17, 2007 04:51 AM
Feed Me, Seymour
bill *at* indcjournal *dot* com
Support Our Advertisers

Search

Archives
June 2008
May 2008
April 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
Extras
PDA

RSD
Atom
RSS 2.0
RSS 1.0

Credits
Movable Type

Our Blogroll