Natron

Natron is a naturally occurring mixture of sodium carbonate decahydrate (Na₂CO₃·10 H₂O, a naturally occurring form of soda ash) and about 17% sodium bicarbonate (baking soda, NaHCO₃) along with small quantities of household salt (sodium chloride) and sodium sulfate. Natron is white to colorless when pure, varying to gray or yellow with impurities. Natron deposits occur naturally as a part of saline lake beds in arid environments. Historically natron had many practical applications which still resonate in the wide modern use of its constituent mineral components. In mineralogy the term natron often means only the prevailing hydrated sodium carbonate found in the historical salt.

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Etymology

The English word natron is a French cognate derived from the Spanish natrón through the Arabic natrun from Greek nitron which derived from the Ancient Egyptian word netjeri, stemming from Wadi El Natrun, Egypt. The modern chemical symbol for sodium, Na, is an abbreviation of that element's new Latin name natrium, which was derived from natron.

Importance in antiquity

Historical natron was harvested directly as a salt mixture from dry lake beds in ancient Egypt and has been used for thousands of years as a cleaning product for both the home and body. Blended with oil, it was an early form of soap. It softens water whilst removing oil, grease and alcohol stains. Undiluted, natron was a cleanser for the teeth and an early mouthwash. The mineral was mixed into early antiseptics for wounds and minor cuts. Natron can be used to dry and preserve fish and meat. It was also an ancient household insecticide.

The mineral was used in Egyptian mummification because it absorbs water and behaves as a drying agent. Moreover, when exposed to moisture the bicarbonate in natron increases pH, which creates a hostile environment for bacteria. Culturally, natron was generally thought to enhance spiritual safety for both the living and the dead. Natron was added to castor oil to make a smokeless fuel which allowed Egyptian artisans to paint elaborate artworks inside ancient tombs without staining them with soot.

Natron is an ingredient for the making of a distinct color called Egyptian blue. It was used along with sand in ceramic and glass making by the Romans and others at least until 640 CE. The mineral was also employed as a flux to solder precious metals together.

Declining use

Most of natron's uses both in the home and by industry were gradually replaced with often closely related sodium compounds and minerals. Natron's detergent properties are now commercially supplied by soda ash (the mixture's chief compound ingredient) and other chemicals. Soda ash also replaced natron in glassmaking. Many of its ancient household roles are now filled by ordinary baking soda, natron's secondary ingredient.

Chemistry of hydrated sodium carbonate

The compound sodium carbonate decahydrate (Na₂CO₃·10 H₂O) found in historical natron has a specific gravity of 1.42 to 1.47 and a Mohs hardness of 1. It crystallizes in the monoclinic-domatic crystal system, typically forming efflorescences and encrustations. Hydrated sodium carbonate effloresces (loses water) in dry air and is partially transformed into the monohydrate thermonatrite Na₂(CO₃)·(H₂O).

Source of soda ash

Hydrated sodium carbonate is stable at room temperature but recrystallizes at only 32°C to sodium carbonate heptahydrate, Na₂CO₃·7H₂O, then above 37-38°C to sodium carbonate monohydrate, Na₂(CO₃)·(H₂O). This recrystallization from decahydrate to monohydrate releases much crystal water in a mostly clear, colorless salt solution with little solid thermonatrite. The mineral hydrated sodium carbonate is often found in association with thermonatrite, trona, mirabilite, gaylussite, gypsum and calcite. Most industrially produced sodium carbonate is soda ash, sodium carbonate anhydrate Na₂(CO₃), which is obtained by calcination (dry heating at temperatures of 150 to 200°C) of sodium bicarbonate, sodium carbonate monohydrate or trona.

Geological occurrence

(List may include sources of either natron or hydrated sodium carbonate)

• Quebec, Canada
  • Rouville County
  • Mont-Saint-Hilaire
• Interior British Columbia, Canada
• Wadi El Natrun, Egypt
• Showa Province, Ethiopia
• Hungary
  • Bács-Kiskun County, (Great Hungarian Plain)
  • Szabolcs-Szatmár-Bereg County (Great Hungarian Plain)
• Campania, Italy
  • Province of Naples
  • Somma-Vesuvius Complex
• Russia (Northern Region)
  • Murmanskaja Oblast
  • Kola Peninsula
  • Khibiny Massif
  • Lovozero Massif
  • Alluaiv Mountain
  • Umbozero Mine
  • Kedykverpakhk Mountain
• England, UK
  • Cornwall
  • St Just District
  • Botallack - Pendeen Area
  • Botallack, and Botallack Mine
• California, USA
  • Inyo County
• Nevada, USA
  • Churchill County (Soda Lake District)
  • Humboldt County
  • Mineral County
• Oregon, USA
  • Lake County
• Washington, USA
  • Okanogan County

See also

Saltpeter