Sodium nitrate

Lore & Background

An early scientific account of the South American deposits was published in 1821 by the Peruvian mineralogist Mariano Eduardo de Rivero y Ustáriz, who analyzed a sample from the Tarapacá district, then part of Peru. The specimen had been supplied by Pedro Fuentes and was held in the Paris laboratory of the mineralogist René Just Haüy. Rivero concluded that the mineral could be used for industrial purposes like glassmaking, fertilizer, and gunpowder, although commercial work did not begin until 1831. The first shipment of saltpeter to Europe arrived in England from Peru in 1820 or 1825, right after that country's independence from Spain, but did not find any buyers and was dumped at sea to avoid customs tolls. With time, however, the mining of South American saltpeter became a profitable business (in 1859, England alone consumed 47,000 metric tons). Chile fought the War of the Pacific (1879–1884) against the allies Peru and Bolivia and took over their richest deposits of saltpeter. In 1919, Ralph Walter Graystone Wyckoff determined its crystal structure using X-ray crystallography.

Reader's Guide

Sodium nitrate has been a key industrial chemical for over a century, primarily sourced from the Atacama desert in northern Chile. Its uses span fertilizers, explosives, glass and pottery enamels, food preservatives, and solid rocket propellant. The development of the Haber process by German chemists Fritz Haber and Carl Bosch allowed synthetic production of ammonia, which was converted into synthetic Chilean saltpeter, leading to a dramatic decline in demand for natural sodium nitrate by the 1940s. Chile still has the largest reserves of caliche, with active mines in locations such as Valdivia, María Elena and Pampa Blanca. The former Chilean saltpeter mining communities of Humberstone and Santa Laura were declared UNESCO World Heritage sites in 2005. Sodium nitrate is also synthesized industrially by neutralizing nitric acid with sodium carbonate or sodium bicarbonate. It is used in thermal energy storage, steel coating, and as a food additive (E251) in cured meats, though health concerns link nitrates and nitrites to increased risks of certain cancers and other diseases.

Did You Know?

• Sodium nitrate is also known as Chile saltpeter, nitratine, nitratite, or soda niter.
• The first shipment of saltpeter to Europe from Peru was dumped at sea to avoid customs tolls.
• Chile fought the War of the Pacific (1879–1884) against Peru and Bolivia to take over rich saltpeter deposits.
• By the 1940s, synthetic production via the Haber process caused a dramatic decline in demand for natural sodium nitrate.