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)

dyeworks at the Gobelins, the royal tapestry factory, and chemists were also employed at two other national enterprises, the porcelain works at Sevres and the Saint-Gobain glassworks. The manufacture of gunpowder, a mixture of sulphur, charcoal and saltpetre (potassium nitrate), was also a state monopoly. Sulphur had to be imported, mainly from the volcanic regions of Italy where it was plentiful, and charcoal, prepared by the pyrolysis of wood, was readUy available in a country with large forests. Saltpetre is formed in the earth wherever there is decaying animal matter such as farmyard manure. We now know that the organic nitrogen is oxidised to the nitrate ion by atmospheric oxygen in the presence of sou bacteria, but in the eighteenth century it was known only that contact with ah was necessary. In France the production of saltpetre was controlled by the gunpowder commission (Regie des Poudres) which had the right to dig suitable soil out of farmyards and other private property, and extract the soluble material with water, yielding a solution that generally contained calcium nitrate, for calcium is present in most soils. On the addition of potassium carbonate, a soluble constituent of wood ash, calcium carbonate was precipitated and the desired potassium nitrate was crystallised and purified. To supplement the supply of saltpetre, artificial saltpetre beds were constructed, in which the raw materials such as manure were mixed with soil in heaps above the ground and exposed to ah. The gunpowder commissioners, one of whom was Lavoisier, published in 1777 an illustrated booklet describing the process, so that private entrepreneurs could produce saltpetre, which they then had to sell to the commission. One such entrepreneur was Guyton de Morveau, who was co-proprietor of a saltpetre bed at Dijon, one of several industrial ventures that he started after retiring in 1782 from his office as public prosecutor in the provincial parlament of Burgundy. Other parts of the chemical industry were also in private ownership. The first sulphuric acid factory in France using the lead chamber process was founded in 1774 near Rouen. By 1789 there were others, one of the most important being at Javel, outside Paris. Sulphuric acid was indispensable in several industries. In tin-plating it was used to remove a layer of oxide from hon before it was dipped into molten tin, and it found another important application in the preparation of nitric and hydrochloric acids from saltpetre and common salt (sodium chloride), both of these being required by metal refiners and assayers. Ah three mineral acids were needed for the preparation of many chemicals used in medicine. Another completely new branch of the chemical industry began as a result of Berthollet's research on chlorine, the gas discovered about 1773 by the Swedish chemist C. W. Scheele. In 1785, in the course of his work at the Gobelins dyeworks, Berthollet investigated Scheele's observation that chlorine had the power of bleaching vegetable colours, and, using an aqueous solution of the gas (chlorine water), found that it could be used for large-scale bleaching of linen, an essential process in textile manufacture. Berthollet did not wish to profit from his discovery, so he published an account of the process and by 1789 several firms were exploiting it commerciaUy. With chlorine water, bleachers were able to achieve in a few days, or even hours, the results that had required several weeks by the traditional process of alternately exposing the linen to ah and sunlight and soaking it in a dilute alkaline solution.