Crystallotechnie

SUBJECT AREA: Chemical technology

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Orphaned at an early age, Leblanc was sent by his guardian, a doctor, to study medicine at the Ecole de Chirurgie in Paris. Around 1780 he entered the service of the Duke of Orléans as Surgeon. There he was able to pursue his interest in chemistry by carrying out research, particularly into crystallization; this bore fruit in a paper to the Royal Academy of Sciences in 1786, published in 1812 as a separate work entitled Crystallotechnie. At that time there was much concern that supplies of natural soda were becoming insufficient to meet the increasing demands of various industries, textile above all. In 1775 the Academy offered a prize of 2,400 livres for a means of manufacturing soda from sea salt. Several chemists studied the problem, but the prize was never awarded. However, in 1789 Leblanc reported in the Journal de physique for 1789 that he had devised a process, and he applied to his patron for support. The Duke had the process subjected to tests, and when these proved favourable he, with Leblanc and the referee, formed a company in February 1790 to exploit it. A patent was granted in 1791 and, with the manufacture of a vital substance at low cost based on a raw material, salt in unlimited supply, a bright prospect seemed to open out for Leblanc. The salt was treated with sulphuric acid to form salt-cake (sodium sulphate), which was then rotated with coal and limestone to form a substance from which the soda was extracted with water followed by evaporation. Hydrochloric acid was a valuable by-product, from which could be made calcium chloride, widely used in the textile and paper industries. The factory worked until 1793, but did not achieve regular production, and then disaster struck: Leblanc's principal patron, the Duke of Orléans, perished under the guillotine in the reign of terror; the factory was sequestered by the Revolutionary government and the agreement was revoked. Leblanc laboured in vain to secure adequate compensation. Eventually a grant was made towards the cost of restoring the factory, but it was quite inadequate, and in despair, Leblanc shot himself. However, his process proved to be one of the greatest inventions in the chemical industry, and was taken up in other countries and remained the leading process for the production of soda for a century. In 1855 his family tried again to vindicate his name and achieve compensation, this time with success.

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