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)

Chlorine was made by the reaction between manganese dioxide (the mineral pyrolusite) and hydrochloric acid, which was itself produced from sulphuric acid and common salt, so it is not surprising that sulphuric acid manufacturers were interested in the new bleaching process. At the Javel factory chlorine was dissolved in a solution of potassium hydroxide, forming potassium hypochlorite, which was a more powerful bleaching agent than chlorine water and had two other advantages: it could be readily transported in glass containers, and it did not emit chlorine gas which badly affected the health of some workers using Berthollet's original process. Both pure and applied chemistry were thus prospering in France before the French Revolution began with the storming of the Bastille on 14 July 1789. A few weeks earlier, Nicolas Leblanc, assisted by M. J. J. Dizé, prepared the first sample of sodium carbonate by a process which became very important in the nineteenth century. Mild soda (sodium carbonate) was a constituent of glass, and, when converted to caustic soda (sodium hydroxide) by boUing with lime water (calcium hydroxide) it was used in the manufacture of soap, much of which was required by the textile industry. The demand for both glass and soap increased rapidly in the late eighteenth century as the industrial revolution gained momentum, but the supply of sodium carbonate was limited in Europe. Some was imported from Egypt, where it occurred in the mineral natron, and more was obtained from the ashes of barilla, a plant that grew on the Mediterranean coast of Spain. After about 1750 chemists recognised that both forms of soda were related to common salt, of which there was an unlimited supply in sea water, and in the 1780's the Society of Arts and Manufacturers in London and the Paris Academy of Sciences each offered prizes for a successful means of manufacturing soda from salt. Various methods were devised in both countries, but the Leblanc process was the first to be a commercial success. Leblanc and Dizé heated salt with sulphuric acid to form sodium sulphate, which was then reacted with charcoal and lime (calcium carbonate) at a high temperature to produce a mixture of sodium carbonate and calcium sulphide, usually containing unreacted charcoal and later known as black ash. Sodium carbonate was separated from the insoluble calcium sulphide and charcoal by solution in water, filtered and crystallized by evaporation. Leblanc's success in the laboratory in 1789 led him to seek financial support to develop a manufacturing plant. Much capital was provided by the Duc d'Orléans, a member of the Royal Family who had long been a patron of the sciences, and in 1790 the construction of a factory began at Saint Denis, ten kilometres north of Paris. By the summer of 1793 about fifteen tonnes of soda had been made, and regular production was about to begin, but then it was interrupted because of political and military developments which seriously affected both pure science and industry. For more that two years after 14 July 1789 the Revolution proceeded in a fairly peaceful manner, while the politicians were trying to turn France from an absolute into a constitutional monarchy, with power shared between the king and the elected National Assembly. At fust it seemed that they would succeed, and