The most informative chemical test of all is simple heating; just warming the sample up and seeing what happens. Some substances, such as naphthalene, melt cleanly to a clear liquid; others, such as sucrose, give a hopeless mess confusing a change of phase with molecular alteration. Daedalus reckons that a shrewd chemist learns more about a material from a melting test than any textbook table tells him.

In 'melting with decomposition' the lattice melts first. The molecules, deprived of lattice support and about to decompose soon anyway, start to break up. The result is a discoloured melt, which, if allowed to cool at that point, gives a coloured solid with decomposed molecules in it. In 'decomposition with melting' the molecules decompose first. The lattice finds itself with nothing to order and falls apart, giving a deeply discoloured liquid that does not resolidify on cooling. This rich mixture melts at a much lower temperature, controlled by the 'lowered mixed-melting-point' principle. Yet textbooks confuse the two effects.

All this matters most, says Daedalus, in the industrial melting of impure mixtures, in particular in the manufacture of carbon fibres. These are made by stretching and heating a chosen pitch or polyacrylonitrile. Daedalus reckons that the ultimate performance of such fibres depends on the amount of polymeric carbon nanotube in them. Such tubes are much stiffer than steel, if not quite as strong for their weight.

If the lattice falls apart first, a useless mass of small molecules results. But if the molecules decompose first, there is a good chance that their product will be carbon nanotube, to be ordered by the surviving, stretching lattice. Polyacrylonitrile, sadly, has to eliminate ammonia to have any chance of forming carbon nanotubes; a tricky reaction. So DREADCO chemists are exploring other carbon-fibre reactions. They are heating polymers such as polyacrylamide and polyacrylic acid derivatives, hoping to find a reaction that gives more carbon nanotube and at a lower temperature. The stretching, orienting lattice could be an entirely different polymer; it might even be good old pitch. If they succeed, stronger carbon composites should soon result. This will lead to better fighter planes and fishing rods, more reliable cases and golf clubs, and stronger cars and computer casings. Even if they fail, Daedalus's chemists will still observe melting points with a clearer insight than current textbooks.