Synthesis of potassium nitrate

Preparation of potassium nitrate

Potassium nitrate is prepared based on different solubility between potassium nitrate, sodium chloride, potassium chloride, sodium nitrate. If a mixture of sodium nitrate and potassium chloride is boiled, the undissolved residue will be sodium chloride, which is the least soluble in hot water of the four possible salts. Meanwhile, potassium nitrate will crystallize when the filtrate is cooled,  since this is the least soluble at the room temperature.

Preparation of potassium nitrate

Preparation of potassium nitrate

At 10° C (g/100ml) At 100° C (g/100ml)
Potassium nitrate 21 246
Sodium chloride 36 40
Potassium chloride 31 56
Sodium nitrate 81 180

190 g of sodium nitrate are dissolved in 200 ml of boiling water in a previously weighed flask. To the boiling solution 150 g of powdered potassium chloride are added and boiled with reflux condenser for half an hour longer. The contents of the flask should at the end weigh 520 to 540 g. While still hot, the solution is rapidly filtered through a Buchner funnel and rinsed with little amount of hot water. The filtrate is rapidly cooled while shaking, and crystalline potassium nitrate starts to form. The mother liquor is evaporated and filtered while hot in order to remove the sodium chloride. The filtrate is rapidly  cooled to obtain more potassium nitrate. The procedure is repeated a few times in the same manner to obtain a further yield. All of the crystals of potassium nitrate are combined and purify them by recrystallization until no chloride ion reaction with silver nitrate is detected. The yield is from 60 to 70% of the calculated.

Laboratory methods of inorganic chemistry by H. Biltz, 122-123, 1928





InChI Key


Canonical SMILES


MeSH Synonyms

potassium nitrate, potassium nitrate monohydrate, saltpeter, saltpetre

Depositor-Supplied Synonyms

POTASSIUM NITRATE, Saltpeter, Nitre, Nitrate of potash, saltpetre, 7757-79-1, Vicknite, Nitric acid potassium salt, Nitric acid, potassium salt, Kaliumnitrat, Kalii nitras, Collo-Bo, Salt peter (VAN), Caswell No. 697, Kaliumnitrat [German], Potassium nitrate(DOT), UNII-RU45X2JN0Z, RU45X2JN0Z, CCRIS 3667, CHEBI:63043, HSDB 1227, Nitric acid potassium salt (1:1), EINECS 231-818-8, NSC 57632, UN1486, EPA Pesticide Chemical Code 076103, AI3-51245, DSSTox_CID_9692, DSSTox_RID_78811, DSSTox_GSID_29692, CAS-7757-79-1, Potassiumnitrate, potassium nitronate, Sensodyne (TN), ACMC-1BIXH, AC1L2NFO, AC1LANK1, AC1Q1TUV, AC1Q1TUW, KNO3, Potassium nitrate [JAN], KSC377C3L, P6030_SIGMA, P8291_SIGMA, Potassium nitrate (JAN/USP), Potassium nitrate [USP:JAN], 12648_RIEDEL, 204110_ALDRICH, 31263_RIEDEL, 542040_ALDRICH, P6083_SIAL, P8394_SIAL, 60414_FLUKA, 60414_SIGMA, 60429_FLUKA, CTK2H7135, FGIUAXJPYTZDNR-UHFFFAOYSA-N, MolPort-003-926-170, s205, 12648_SIAL, 31263_SIAL, 221295_SIAL, Tox21_201581, Tox21_303394, AKOS015902862, AKOS024418772, LS-3214, RTR-024775, NCGC00249235-01, NCGC00257274-01, NCGC00259130-01, BP-31027, E252, Potassium nitrate [UN1486] [Oxidizer], Potassium nitrate [UN1486] [Oxidizer], TR-024775, C13557, D02051, EC 231-818-8, 3B4-1829, I14-19707, 96193-83-8

Removed Synonyms

Niter, Salt peter, Niter (VAN), potassium nitrate monohydrate, CHEMBL1644029, CID24434, C023844

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