The following text is for questions 74 to 76.
 

    TNT was first made in 1863 by a German chemist, Joseph Wilbrand. He was trying to make a dyestuff, and TNT is yellow in colour. It was nearly 20 years before it was discovered to be an excellent lent high explosive. At that time, 2,4,6-trinitrophenol, a molecule with a similar structure, was the best high explosive around. Better known as picric acid, it had a downside, as dry picric acid is very shock-sensitive. Moreover, it's acidic, so that it slowly corroded metal casings, forming metal salts that are even more shock-sensitive than the free acid.

    TNT had several advantages over other explosives. Although it is not as strong a n explosive as picric acid, it was much safer to handle and harder to detonate. Because of its melting point of only 80°C, it became possible to fill shells safely with molten TNT. The German military started using TNT as their standard explosive in 1902, whilst the British stuck with picric acid, a choice with unfortunate consequences.

    TNT-filled shells are more likely to penetrate armour before exploding, and they also produce a very high-velocity shockwave. In contrast, shells filled with the more sensitive picric acid did not penetrate armour, but exploded on contact, causing less damage. This was part of the reason for the Royal Navy suffering greater losses than the Germans at the Battle of Jutland in 1916.

    The first world war resulted in an intense demand for toluene, which was not just needed for the manufacture of TNT, but was also involved in the synthesis of many dyes. The problem was solved by the adoption of amatol as a high explosive, a mixture of 80% ammonium nitrate with 20% TNT. This not only helped the toluene go further but had an added bonus. One disadvantage of TNT is that the molecule does not contain enough oxygen to oxidise all the carbon and hydrogen it contains, so a TNT explosion is accompanied by a black cloud of carbon. Ammonium nitrate is an oxygen-rich explosive, producing more oxygen than it needs, and thus giving a white smoke rather than the black clouds associated with TNT.

The paragraph following the passage most probably discusses ....