There are no X-Ray machines in existence that can detect the chemical composition of a liquid. None. Nada. That's not what X-rays do.

There ARE machines out there that can - these are separate add-ons and I blogged about them here (even providing a link to the vendor) almost two years ago. They are not overly expensive, can test without a sample prep, are highly accurate and require little in the way of passenger inconvenience.

I believe the TSA has bought a few of these, or similar machines for testing - but in no way does the X-ray portion of the bag screening device or any of the standard X-ray devices there which lack this add-on detect the presence of a binary explosive compound.

I didn't say the TSA wants a cargo-sourced incident - but their ridiculously unbalanced approach to threat management clearly indicates to me that an incident caused by a cargo explosive is not on their list of priorities, and it should be their number one priority as it's the easiest attack to carry out.

The entire TSA security apparatus is focused on three things:

1. prevent another 9/11
2. prevent another shoe bomber
3. prevent a liquid bomb attack

1. has already been taken care of by procedural and structural changes. 2. is not a credible threat, and it's a threat that could manifest itself in any number of places other than shoes, and 3. was never a credible threat to begin with - the science has proven that it's functionally impossible to prepare a liquid bomb on board or to prepare it ahead of time and transport it to the aircraft without it either detonating ahead of time or going benign en route.

These 'controlled lab' demos to "prove" the viability of a liquid explosive are nonsensical when applied to a non-controlled test.