Sodium nitrate can be combined withÂ sulfuric acidÂ to produceÂ nitric acid, which is distilled off. At lower pressure the lower temperature needed results in less decomposition. The theoretical 2 moles of nitric acid per 1 mole ofÂ sulfuric acidÂ results in a very high end temperature, much decomposition and a solid neutral sulfate that is difficult to remove. When this reaction was important industrially, it was common practice to operate withÂ sulfuric acidÂ in excess to end on a mostly bisulfate product poured molten out of the retort.
HobbyistÂ gold refiners use sodium nitrate to make a hybridÂ aqua regiaÂ that dissolves gold and other metals.
Less common applications include as an oxidizer in fireworks, replacingÂ potassium nitrateÂ commonly found inÂ black powder, and as a component in instant cold packs.
Sodium nitrate is used together with potassium nitrate andÂ calcium nitrateÂ for heat storage and, more recently, forÂ heat transferÂ inÂ solar powerÂ plants. A mixture of sodium nitrate, calcium nitrate and potassium nitrate is used as energy-storage material in prototype plants, such asÂ Andasol Solar Power StationÂ and the Archimedes project.