Calcium nitrate, also called Norwegian saltpeter (Norgessalpeter), is the inorganic calcium compound with the formula Ca(NO3)2.
Calcium nitrate is a source of both calcium and nitrate ions in reactions. Because of its hygroscopicity, it is unsuitable for use as an oxidizer in energetic mixtures; however, due to the insolubility of many calcium salts, the nitrate ion in calcium nitrate can easily be used to prepare other more useful nitrates as well as other calcium compounds. Examples of this include the addition of sodium carbonate to precipitate calcium carbonate and leave sodium nitrate in solution, or the addition of potassium sulfate to generate potassium nitrate in solution, precipitating calcium sulfate. Virtually any nitrate compound can be produced by addition of a sulfate or carbonate solution in this manner.
Calcium nitrate is a white, hygroscopic solid. It presents itself as a tetrahydrate. Calcium nitrate is extremely soluble in water. The dissolution of calcium nitrate tetrahydrate in water is highly endothermic, making it useful in cooling baths. It is also soluble in alcohol and acetone, but insoluble in concen. nitric acid.
Calcium nitrate can be bought as a fertilizer, often for hydroponics. It is fairly pure, unlike ammonium nitrate which usually contains calcium sulfate to reduce its explosive hazard. However it can also be found together with ammonium nitrate, and that fertilizer is known as calcium ammonium nitrate.
Because of its hygroscopicity, it cannot sustain an energetic mixture like other nitrates, such as potassium nitrate can, making it useful as a safe nitrate ion source. Skin contact with the anhydrous compound should be avoided as it can be irritating.
Calcium nitrate hydrate should be stored in closed bottles, in a place with low moisture. The anhydrous form should be stored in sealed bottles, as it is hygroscopic.
Calcium nitrate without toxic impurities can be safely dumped in the environment, as it has low toxicity and it is a nitrogen source for plants. Avoid dumping large amounts though.