Unless you are in the habit of reading the ingredients list on your laundry detergent, you are not likely to be familiar with sodium carbonate. Yet this industrial chemical of great importance has a fascinating history. So important that in 1775 the French Academy of Sciences offered a prize to anyone who could develop an efficient process for producing this substance, commonly known as 鈥渟oda.鈥澛�
Sodium carbonate was invaluable in the production of soap and glass. To make soap, sodium carbonate is combined with animal or vegetable fat, and to make glass it is heated together with sand. Both these processes have a long history and until the 18th聽century relied on isolating sodium carbonate from ashes left behind when plant substances were burned. However, as the demand for soap and glass increased, a more abundant source of soda was required, and the French Academy of Sciences offered a prize to anyone who could produce it from salt, which was cheap and readily available.聽
Nicolas Leblanc, a French physician took up the challenge, having developed an interest in chemistry while studying medicine. He succeeded in producing sodium carbonate from salt by a two-step process. First, salt was heated with concentrated sulfuric acid, producing sodium sulfate and hydrogen chloride gas. The sodium sulfate was then crushed and heated with charcoal and limestone (calcium carbonate) to yield sodium carbonate. With his patron, the Duke of Orleans, Leblanc established a factory for making sodium carbonate and claimed the prize that had been offered. However, he never did collect. The French Revolution got in the way, the Duke was accused of 鈥渞oyalism鈥� and was guillotined. Leblanc鈥檚 factory was taken away and nationalized with the Committee of Public Safety forcing Leblanc to publish details of his process without any compensation.聽
Eventually when Napoleon came to power, the plant was returned to Leblanc but no funds were allocated for restoring it to operation. A desolate Nicolas Leblanc committed suicide. His process, however, was eventually put into production by European chemical plants, making sodium carbonate readily available. The glass and soap industries prospered, as did others like paper manufacture that had come to rely on soda.
In England, Leblanc鈥檚 process provoked one of the first environmental protection acts ever introduced. The hydrogen chloride released in soda manufacture caused problems as it dissolved in rainwater to form hydrochloric acid, resulting in significant acid rain. The 鈥淏ritish Alkali Act鈥� required soda manufacturers to pass their effluent gases through acid-absorbing towers. But this did not solve all the environmental problems introduced by the Leblanc process, since calcium sulfide, another byproduct, was dumped in fields where it slowly released toxic and foul-smelling hydrogen sulfide. Today, the Leblanc process has been replaced either by the Solvay process which is more efficient at making soda from salt, or by isolating soda from mineral deposits known as trona, found abundantly in Wyoming. Still, the Leblanc process retains its historic significance as the first commercial method of making sodium carbonate, a critical industrial chemical.聽
Why is it in your detergent? Two reasons. A solution of sodium carbonate is alkaline, and greasy stains are better removed in an alkaline solution as insoluble fats are converted to soluble sodium salts of fatty acids. In addition, sodium carbonate softens water. 鈥淗ard water鈥� contains calcium and magnesium ions that bind with detergent molecules and reduce their ability to form suds that help remove stains. In the presence of sodium carbonate, calcium and magnesium ions form calcium and magnesium carbonates, both of which are insoluble and precipitate out of solution, thereby enhancing the cleaning ability of the detergent, giving meaning to the term 鈥渨ashing soda.鈥�
So, next time you wash yourself with soap, launder your clothes, or take a swig of water out of a glass, think of sodium carbonate and its enthralling history.
