Sodium nitrate, birefringence

Nitrates and Their Properties. Sodium nitrate, NaNOj, forms colorless crystals closely resembling crystals of calcite, CaCOg (Fig. 9-2). This resemblance is not accidental. The crystals have the same structure, with Na+ replacing Ca++ and NO3- replacing 003 The crystals of sodium nitrate have the same property of birefringence (double refraction) as calcite. Sodium nitrate is used as a fertilizer, and for conversion into nitric acid and other nitrates. 

---