Chemically pure sodium nitrate can be obtained by repeated recrystallization of Chile saltpetre or by synthesis.
This is filtered, washed, and then fused with caustic soda, when the sulpho-group is replaced by a hydroxyl group, and a second hydroxyl group is simultaneously formed; in order to render the formation of this second group easier, a little potassium chlorate or sodium nitrate is added to the reaction mixture.
The more important are as follows: by decomposing strongly heated sulphuric acid in the presence of a contact substance; by heating an intimate mixture of one part of sodium nitrate with two parts of zinc oxide (T.
Fuming nitric acid consists of a solution of nitrogen peroxide in concentrated nitric acid and is prepared by distilling dry sodium nitrate with concentrated sulphuric acid.
For sodium nitrite see Nitrogen; for sodium nitrate see Saltpetre; for the cyanide see Prussic Acid; and for the borate see Borax.