A cocktail of household ingredients mixed together in the right concentration and quantity is enough to create a powerful explosion.

Recipes for these home-made bombs are easily accessible on so-called cookbooks' on the internet which recommend a mixture of water, petrol, ammonium nitrate (found in fertilizers), sulphuric acid and sodium hydroxide (caustic soda). Adding a solid, slow-burning fuel like rubber or polystyrene would also make the explosion more powerful.

But Huw Jones, a lecturer in chemistry, environmental science and public health at Middlesex University, said in handling explosives in his own home, Shanker Venkatesan was playing a dangerous and, in this case, lethal game.

"Anyone can follow a recipe on the internet, like following a cookbook recipe, but you have to have some expertise," he said. "You need to know some chemistry to know the potential hazards along the way. It's not the sort of thing just anyone could do."

A licence is needed to get hold of the chemicals in a pure form, and tabs are kept on anyone buying them, while purifying fertilizers outside of a laboratory could result in an uncontrolled explosion on its own.

Mr Jones also said that if an inexperienced chemist used the right ingredients in even slightly wrong concentrations or amounts, the whole mixture could explode without warning.

"It's not straightforward, and it isn't true that it is easy to do," he said. "You would have to be well informed, on the theoretical side as well as on the practical side."

August 21, 2002 17:00