Nicolas Leblanc (1742–1806)

Nicolas Leblanc had a formative influence on the early chemical industry. In 1787 he devised the process for making alkali that dominated production in the nineteenth century. Alkali was used in manufacturing glass, soap, paper, metals, textiles and other products that required acid to be neutralized. Before his process, alkali was produced from organic sources such as seaweed, the barilla plant or wood ash; however the raw material for Leblanc’s process was salt. It was an invention of huge importance, thought it brought Leblanc only personal tragedy.

Leblanc was not an industrialist but a physician. He was born in Cher, in the centre of France, where his father was an official at an ironworks. He studied medicine and chemistry in Paris and qualified as a surgeon. In 1780 he was appointed private physician to Duc Louis-Phillipe d’Orléans, who let Leblanc use his private laboratory for experiments. The problem of alkali supply was already recognised and in 1775 the French Académie des sciences offered a prize for a solution. Many people had studied it but in 1791 Leblanc made his breakthrough, using sea-salt as his raw material. He was granted a patent but was never paid the prize money.

The process involved two stages. The first was to treat common salt with sulphuric acid in a cast-iron pot to form sodium sulphate (NA2SO4). This released hydrochloric acid gas into the atmosphere. The second stage was to heat the product in a furnace with coal and limestone to make crude sodium carbonate and calcium sulphide. The sodium carbonate was dissolved in water and evaporated to produce anhydrous sodium carbonate (NA2CO3) – also known as ‘soda ash’.

Leblanc set up a plant with the Duc d’Orléans. However, the Revolutionary government in France confiscated it shortly afterwards, annulled his patent and sent the Duc to the guillotine. The plant was finally returned to Leblanc nearly a decade later but by now he was without funds and his applications for compensation failed. Aged 63, he shot himself.

From 1807, the process was copied by industrialists in the north of England, first near Newcastle and later near Liverpool: regions where sea salt and coal were readily available. By 1880, 120 works in Britain used it. Initially, the biproducts were discarded but other uses were found for them as the chemical industries developed. However, the Leblanc process was a cause of severe atmospheric pollution. In the late nineteenth century it was superseded by the Solvay process and later by electrolysis.