Salt also has industrial uses. The chemical industry and snow removal are two activities particularly greedy for salt, but so are other sectors such as the pharmaceutical industry.
Salt is one of the basic natural resources required for the chemical industry since it furnishes this sector with two essential substances: chloride and caustic soda. They are obtained via a chemical process called electrolysis which separates the chloride and sodium components of salt (see Geology, 1st paragraph). Thus formed, these two substances are then used to make numerous products: plastics, disinfectants and whiteners, detergents, wood pulp for paper, colouring for paints, artificial textile fibres, etc.
The Solvay factory in Tavaux (near Dole in the Jura department) is an example of local salt exploitation for industrial and chemical purposes. It produces chloride from salt taken from the underground strata of rock salt. Extracted from the subsoil by dissolution, the salt is transformed into brine and transferred to the factory through a pipeline. The current pipelines extend over more than 100 kilometres, from the municipalities of Etrez and Marboz located north of Bourg-en-Bresse. The factory uses 700,000 tons of salt every year.
Another major use of salt today is for winter maintenance of road systems. It actively prevents the formation of ice on the roads by lowering the freezing point of water. Salty water only freezes at -7 or -8 ° Celsius instead of 0°. When temperatures fall below these levels, salt is combined with other products to lower the freezing point even further.
Spreading salt on the roads is a relatively recent practice in history. It goes back to the 1880s in Paris. City employees went through the streets with their wheel barrows and shovels to spread salt. Modern practices appeared in 1968 during the winter Olympic Games in Grenoble which was the first large-scale test of the technique. Since then, the wintertime salting of roads has greatly developed and requires more than a quarter of the salt sold in France today.
Better known in granular form, salt can also be used as brine or a mixture of brine and grain. In Salins-les-Bains, the town uses its own local source of salt; the streets are treated with brine drawn from a former well of the saltworks, the well of Amont.