The Romance of Modern Chemistry

GREAT DISCOVERIES lowered and the level of the water rose. Thus it was that the use of a cracked vessel instead of a sound one led on to Graham’s famous investigations on the diffusion of gases. A more recent and equally striking instance of a breakage leading directly to a valuable discovery has been recorded in connection with the manufacture of artificial indigo—a manufacture which, as we have already seen, famishes a conspicuous case of the chemist’s successfill attempt to build up natural products, and to compete with Nature herself. One of the most important steps in the manufacturing process is the production of phthalic acid from naphtha- lene—the chief raw material of synthetic indigo. This change can be effected by the action of hot sulphuric acid upon naphthalene, but only slowly. In the course, however, of experiments carried out with the object of improving the method of converting naphthalene into phthalic acid, the bulb of a thermometer was accident- ally broken, and the mercury ran out into the heated mixture. It was at once noticed that in presence of mercury the conversion of naphthalene into phthalic acid was much accelerated, and this chance observation led at once to the desired improvement of the process. The use of mercury at this stage of indigo manufacture is now an established custom. The reader must, of course, remember that without adequate knowledge on the part of the investigator and without keenness of observation these chance occurrences would have been of no account The observer, even supposing he has the necessary equipment, must always be on the look-out for what is strange and unexpected, always eager to see Nature in unfamiliar garb. 839