by CKR
We’re getting lots of hits from The Next Hurrah and from Google searches on various aspects of liquid explosives. Welcome to the newcomers—check out WhirledView! Backtracking those searches, I find that there is relatively little useful discussion on the Web about what might have been used in that foiled plot.
So I’ll summarize my somewhat cranky previous post and add some things, along with tentative conclusions.
It appears that no materials have been found that the plotters might have used in attacks on airplanes. Over the weekend, Brian Ross reported this, and Secretary Michael Chertoff evaded questions in a way that was consistent with this. However, it might be prudent at this time not to be forthcoming about what has been found. I don’t understand British law well, but I know that they require that much less be said about pending court cases than we do in the US, so that alone could be a reason for not saying much on this subject.
As to the explosives that might be used, I have to admit that I hadn’t paid much attention to TATP (triacetone triperoxide) until a year or so ago, so most of what I know is from the internet. I can make some guesses about its preparation and properties, though, because chemistry does work the same in the United States and Britain, and in in jetliners over the Atlantic.
The news reports are not at all consistent. So let’s start with Wikipedia. Nothing in the article looks obviously incorrect to me.
TATP is a solid (not a liquid!). The article doesn’t give any numbers for its sensitivity, but says it is more sensitive than nitroglycerin. It also says that it may have been the explosive used in the July 2005 London bombings and in Richard Reid’s shoes.
Like many other explosives, several forms of varying sensitivity may be produced. The most sensitive will be the most important, because if it detonates, the others will go along with it.
Most detection of explosives depends on their containing nitrogen. TATP contains no nitrogen and is therefore not detectable by these methods. However, I saw a laser method over the weekend that I would expect to be adaptable to TATP.
Wikipedia says that TATP sublimes, leaving a more sensitive product. I would also expect it to decompose in air, probably to harmless products. The Wikipedia article also refers to a general property of explosives: they may burn in the open but explode if they are confined.
Wikibooks provides a synthesis. Think recipe. The safest and most effective way to prepare a chemical, particularly an explosive, is usually not obvious and usually requires more than just pouring two liquids together.
I haven’t synthesized explosives, but I have worked with chemical recipes. One, for a zeolite catalyst, worked exactly right the first time and gave me a better product than a commercial sample. Another, an analysis method, needed three months of work before it gave me anything like consistent results. The equivalent of those three months, with TATP, would yield a few explosions. The neighbors might just notice.
There are a couple of other recipes on the Web, pretty much like the one in Wikibooks, although little differences in recipes can make big differences in outcome. They all require handling of concentrated hydrogen peroxide, which has its own problems, cooling, and addition of sulfuric acid with continuous stirring with an automatic stirrer, which the plotters might find inconvenient in an airplane restroom. Adding concentrated sulfuric acid to a solution heats it up, so active cooling (lots of ice cubes or laboratory equipment, again) is required. The crystals take hours to precipitate out, and then you have to filter and dry the crystals. Somewhere along the way, someone on an airplane might just notice all that.
There’s good old nitroglycerin, too, which I would also expect to cause some random explosions during preparation. Gasoline, if allowed to evaporate, can cause serious explosions. My father once poured a quarter-cup of gasoline down a gopher hole, let it evaporate and set a match to it. It shook him up enough that he didn’t do it again. I don’t know what happened to the gopher. So gasoline shouldn’t be allowed on planes. It also does not contain nitrogen and so might be difficult to detect.
However, all these things have funny smells, even pungent and nasty. I would expect that airport dogs are trained on them.
I don’t see anything so far that justifies the uproar, but we should be hearing more over the next days and weeks.
Update (8/17/06): I've done some googling. Results here.