Technikatörténeti szemle 19. (1992)

KÖNYVISMERTETÉS - Papers of the First „MINERALKONTOR” International Conference on the History of Chemistry and Chemical Industry (Veszprém, 12-16 August, 1991)

In order to oncrease the production of munitions the scientific members of the Committee of Public Safety called on their fellow scientists to abandon their normal research and apply their talents to urgent technical problems. This .mobilisation of the scientists' set a pattern that was followed in several countries during the two world wars of the twentieth century. • Too little saltpetre was being produced to supply gunpowder for the new armies, so early in 1794 the Convention distributed a reprint of the instructional booklet published by the gunpowder commission in 1777. It also organised in Paris a series of intensive ten-day courses in which eleven hundred men from all parts of France were taught how to make saltpetre. Lectures and demonstrations were given by well known chemists, including Guyton and Fourcroy, both of them now members of the Convention though Guyton was no longer on the Committee of Public Safety, and at the same time a course on the manufacture of cannons was given by Gaspard Monge, who had been a professor of mathematics and physics at the former college for military engineers at Mezieres. When the eleven hundred men returned to their homes France became a great arsenal, producing the weapons and ammunition that saved the Republic. The manufacture of saltpetre and cannons was often carried out in churches, which were no longer used for religious services as the Convention had become very anti-religious by 1794. Charcoal was made on a larger scale than previously but sulphur had to be used sparingly until its importation could be resumed after 1795, when the military situation improved. Cannons used by the army were generally made of gun-metal, an alloy of about nine parts of copper and one part of tin. France had few oras of these metals, but large quantities were available in the bells hanging in the disused churches, and these bells were removed by order of the Committee of Public Safety, often in the face of opposition from the local people. Bell-metal is also a copper-tin alloy, but it contains far more tin than gun-metal does, and it is too brittle for use in guns. It was necessary to remove most of the tin, and a satisfactory process was devised by Fourcroy. He knew that tin was more easily oxidised by atmospheric oxygen than copper, so by keeping the molten bell-metal in contact with ah under carefully controlled conditions he succeeded in removing most of the tin as oxide. This left an ahoy suitable for guns, or even pure copper, which was used for plating ships' hulls. This episode is interesting, because it represents an early application of science to a metallurgical process. However, the chemists were not always successful during the critical years of 1793—4. An attempt was made to improve the gunpowder supply by replacing potassium nitrate by potassium chlorate, a compound discovered by Berthollet in 1787, but it is much more reactive than the nitrate, and the experiments had to be abandoned after several fatal explosions. As well as guns and powder the armies needed large amounts of leather, some for the soldiers' boots but more for the horses' harness, since all land transport was horse-drawn. Leather is made from animal hides by tanning, a process that required the hides to be treated with various organic materials over a long period of time. In 1794 Armand Seguin, a young chemist who had worked with Lavoisier, developed a much faster process involving sulphuric acid, which was permitted to be used for this purpose.