Chemists have developed a spray that can instantly identify bomb-makers. The main ingredient turns red when it comes in contact with a common improvised explosive. Soldiers or police can wipe the skin of a terrorism suspect with a sterile cloth; wet it with the detector chemical; then watch for a blood-like hue.

Urea nitrate is an easy-to-make explosive that has claimed over one hundred lives during terrorist attacks in Israel. Noah Shachtman recently mentioned that he saw the nefarious substance in an Iraqi-made IED. In a recent post at Danger Room, he said, "To get ahead of insurgents, coalition forces have to figure out who's really building and planting the bombs." For these reasons, a quick and dirty way to catch terrorists red-handed will be tremendously useful.

In the September issue of the Journal of Forensic Sciences, Joseph Almog and his team at the Hebrew University of Jerusalem explained how their bomb-detecting chemical works.

Trained in organic chemistry, Almog has a long history of inventing color-changing test fluids for law-enforcement. The former brigadier general assisted Shmuel Kraus and Baruch Glattstein with the development of Ferrotrace, a chemical that turns dark-violet when sprayed on hands that have recently held a pistol or grenade. He has also invented an agent that reveals hidden fingerprints and a kit that can identify a wide variety of explosives.

In order to improve upon their newest product, Almog and his team needed to understand exactly how it changes color. To do that, they took a picture of the indicator chemical as it interacted with urea nitrate.

Creating a picture of individual molecules is not easy. The researchers grew crystals from the red dye and then carefully inserted one of them into an x-ray diffraction machine (not the same as a medical x-ray). This created a blurry, 3-D image that the scientists sharpened by using a sophisticated computer program as a sort-of digital lens – bringing it into focus.

With this new insight, and a forensic chemistry program founded by Almog, the Hebrew University may be a wellspring of bomb-detection technology for years to come.