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chocolate bombs III

OK finally I am going to make something blow up with chocolate, I am going to stuff my mouth with chocolate until I explode. OK that it is the closest I am getting to a bomb powered by chocolate.

So far I imagine you have learned a few useful things about chemistry and physics. Such as the amount of chemical energy can not be used to predict how good something will be as an explosive and something about nuclear reactions.

Now we are going to learn something about X-ray equipment. The X-ray equipment used for bone density measurements and for airport security often uses dual energy technology to get more information about the objects (or people) being checked. (http://www.feelsafer.com/rapidscan-xray.html and http://www.rapiscansystems.com/datasheets/Rapiscan-620DV-Brochure.pdf).

One person recently remarked online that they had a bar of chocolate in their bags and the airport X-ray machine thought it was part of a bomb. Let us consider what might have been going on.

If we consider TNT as a classic explosive then we will find that the density of TNT is 1.655. We can calculate this from the crystallographic details of TNT. The orthorhomic version of TNT has a unit cell which is 6.077 by 14.911 by 20.017 Å. Thank goodness being orthorhomic all the angles of the cell are 90 degrees. (Be thankful for small mercies !). We can later recalculate the density based on this data and the fact that Z is 8. (See W.R.Carper, L.P.Davis, M.W.Extine, J. Phys. Chem., 1982, 86, 459).

I can not recall the density of chocolate from memory, so I will have to guess that it is similar to TNT. I assume that chocolate is similar to glucose in density (1.528). As TNT contains CHNO and chocolate is made of CHO then the two will have very similar X-ray absorption properties. Thus a dual energy X-ray machine will think that both will look the same.

I may go through the TNT density example soon with you.

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