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Sources of Sodium Nitrate

Sodium nitrate is a white, odorless chemical compound having cubic crystals. It also is known as Chile saltpeter or Peru saltpeter. Sodium nitrate, found in large natural deposits, is similar to potassium nitrate in most of its chemical properties and physical appearance. It can be produced synthetically to some extent during chlorine production, in which sodium nitrate is obtained as a byproduct.

  1. Natural deposits

    • Sodium nitrate occurs as large natural deposits in arid regions along the western coast of Latin America, especially near the boundaries between Chile, Peru and Bolivia. Caliche, the crude nitrate-bearing rock, is situated at a depth of about 10 feet and extends up to 50 feet below the Earth's surface. The area of a sodium nitrate deposit can be up to 220 miles in length and 2 miles in breadth. The caliche found very near to the surface usually is associated with a considerable amount of clay, sand, rock debris, sodium sulfate, chloride and a little iodide. It usually is found in sheets. Caliche is tinted yellowish-white to gray or brown and contains about 20 to 55 percent sodium nitrate.

    Chile Saltpeter

    • Until the 1940s, the Atacama Desert of Chile was the world's largest natural reserves of caliche ore. More than a century old, this mine is no longer an active; its value decreased substantially in the first decades of the 20th century. However, Chile still retains the largest deposits of caliche, with several active mines in places like Pampa Blanca, Maria Elena and Pedro de Valdivia.

    Recent Excavations

    • Some very high quality, large deposits of caliche have been discovered in the trans-Caspian region and upper Egypt, but they do not have as high a yield as Chile. These beds were formed from the decomposition of sea plants.

    Production Using Crude Caliche

    • The ore caliche is ground and boiled with water. This mother liquor contains most of the iodide, chloride, magnesium and nitrate. It then is allowed to go through the iodine recovery process so the remaining solution contains only nitrate, which is washed with fresh water yielding a weak solution. This is then dried, and crystals of sodium nitrate are separated out. They are further dried in sunlight.

    Synthetic Production

    • Sodium nitrate is synthetically produced in small amounts by the action of nitric acid on a sodium carbonate or sodium hydroxide solution.

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