Widespread speculation on the chemistry of liquid explosives, following news of a terrorist plot to blow up transatlantic flights from the UK, must be treated with caution.

Widespread speculation on the chemistry of liquid explosives, following news of a terrorist plot to blow up transatlantic flights from the UK, must be treated with caution, warn leading chemists. 

Wildly differing media reports suggested that substantial quantities of nitroglycerine, a liquid explosive, could be easily smuggled onto a plane, while others preferred the idea that terrorists were planning to make the solid explosive triacetone triperoxide (TATP) from liquid ingredients in aircraft toilets. TATP was used in the London Underground bombing campaign of 7 July last year.

The frenzy followed an announcement from the Metropolitan Police Service, London, UK, on 10 August, that it had successfully disrupted ’a major terrorist plot to allegedly blow up an aircraft in mid-flight’. The Department for Transport followed the news with instructions that ’any liquids discovered must be removed from the passenger’.

’The measures that are in place are appropriate,’ said Sean Doyle, head of chemistry and research at the forensic explosives laboratory of the Defence Science and Technology Laboratory (DSTL), Fort Halstead, UK. ’There is a real threat’, he told Chemistry World, adding that his team - which worked on samples from last year’s London bombs - was ’very much at the heart of the investigation.’

DSTL subsequently confirmed that it is currently analysing samples relating to the investigation, although as Chemistry World went to press security officials said they could not confirm that explosives had been recovered.

This means that the identity of the alleged explosive liquid is far from clear. ’There are liquid explosives, there are materials that are liquid that you could mix to make explosives, and there are liquids that you can combine to produce something like TATP,’ said Gerry Murray, of the Forensic Science Agency of Northern Ireland.

Peter Fielden of the University of Manchester, UK, who works on explosives detection with DSTL, said he was concerned about the media attention the explosives were receiving. ’There’s an awful lot of unknowns and a great deal of speculation,’ he said. 

Nitroglycerine would cause terrorists a big practical challenge if they wanted to get enough on board to explode an aeroplane, said John Wyatt, a former bomb disposal officer and security consultant. Wyatt was head of counter-terror search operations in the UK during the era that followed the Brighton hotel bombing in 1984.

’You literally just have to drop [nitroglycerine] and it’ll explode,’ he said. ’The impact of going through an x-ray machine or the impact of a body search is likely to set the stuff off.’

Wyatt said that while various combinations of fuels and oxidisers could be used to produce an explosive, preparing them is an extremely delicate process. One of the best known combinations is nitric acid and nitrobenzene: ’but to suggest that someone’s going to walk on to an aircraft and mix these two together to get an explosive liquid is, to put it bluntly, nonsense.’

Reports of making TATP in the toilets are equally far-fetched, said Murray. ’It would be extremely difficult to make [TATP] on a plane,’ he said, not least because the process must be carried out at low temperature. ’It’s not just a question of mixing A and B and getting the stuff out at the end.’

Bea Perks  and Katharine Sanderson