The purification process of sodium (or potassium) nitrate present in saltpeter fertilizers can be done by the crystallization technique using water as a solvent. We use 50 mL of water for 90 grams of fertilizer. And as a result we obtained 39.7 grams of sodium nitrate, which corresponds to a yield of 44%.

Once the solution starts to boil it is important to filter it, otherwise a lot of water will evaporate and there will be little solvent, which reduces the yield.

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References

LIDE, R. D. Handbook of Chemistry and Physics. 87th Edition, 2006-2007.

ARMAREGO, W. L. F.; CHAI, C. Purification of laboratory chemicals. 5a.ed. Burlington, USA: Elsevier:
Butterworth-Heinemann. 2003.

PATNAIK, P. Handbook of Inorganic Chemical Compounds. New York: McGraw-Hill, 2003.