Potassium nitrite ( potassium nitrite ) is a potassium salt of nitrous acid with the formula K N O 2 . It is a white or slightly yellowish crystalline hygroscopic powder. Very soluble in water. In air, it slowly oxidizes to potassium nitrate KNO 3 . Food supplement E249. It is used as a coloring improver and preservative in the food industry in meat and fish products.
| Potassium nitrite | |
|---|---|
 | |
 | |
| Are common | |
| Systematic name | Potassium nitrite |
| Traditional names | Potassium nitrate |
| Chem. formula | Kno 2 |
| Physical properties | |
| condition | transparent (white) crystals |
| Molar mass | 85.10 g / mol |
| Density | 1.915 g / cm³ |
| Thermal properties | |
| T. melt. | 387; 440; 441 |
| Chemical properties | |
| Solubility in water | 280 0 ; 413 100 g / 100 ml |
| Solubility in ethanol | dissolves |
| Classification | |
| Reg. CAS number | 7758-09-0 |
| PubChem | |
| Reg. EINECS number | |
| Smiles | |
| Inchi | |
| Codex Alimentarius | |
| RTECS | |
| ChemSpider | |
Properties
Potassium nitrite forms colorless or slightly yellowish highly hygroscopic crystals, monoclinic syngony , space group I m , cell parameters a = 0.677 nm, b = 0.499 nm, c = 0.445 nm, β = 101.75 °, Z = 2.
Very soluble in water, dissolution is accompanied by a decrease in temperature. The solution has a slightly alkaline reaction due to anion hydrolysis .
The crystals are destroyed at 360 ° C (until a melting point of 440 ° C or 441 ° C is reached, at 100 KPa according to Polish and English Wikipedia and 438 ° C at a pressure of 101325 Pa [1] , the melting enthalpy is 17 kJ / mol [1] ).
Above this temperature, it decomposes according to the scheme:
Like sodium nitrite, it is an oxidizing agent, especially at elevated temperatures, and reacts with metals such as aluminum (especially in powder form), dehydrated ammonium compounds such as ammonium sulfate , cyanides, and many organic compounds.
In air, it slowly oxidizes to potassium nitrate. :
Nitrites can be detected by a characteristic reaction with iron (II) sulfate in the presence of concentrated sulfuric acid (by the formation of a brown color).
Being in nature and methods of obtaining
In nature, nitrites appear at intermediate stages of the nitrogen cycle, both during nitrification (nitrogen attachment to compounds) and denitrification (nitrogen detachment from compounds). In industry, potassium nitrite is obtained by the reaction of nitrogen oxides with potassium hydroxide .
It turns out during the oxidation of lead by potassium nitrate:
or during thermal decomposition:
Application
- Potassium nitrite as a food additive E249 (preservative) is used similarly to other nitrites and salts (sodium chloride and sodium nitrite) - prevents the formation of botulinum toxin (formed during the life of the stick Clostridium botulinum ). When added to meat, it forms nitrosomyoglobin , which has a characteristic red color, which can be observed in most foods (sausages, sausages, etc.). The use of products containing potassium nitrite causes thirst.
- In the European Union, the sale of potassium nitrite for food purposes is permitted only in the form of a mixture with edible salt, with a nitrite content of about 0.6% [2] . Since 2013, similar rules have been in force in Russia.
- Potassium nitrite is used for diazotization in the production of azo dyes.
- Potassium nitrite is used in analytical chemistry to recognize amines.
- Potassium nitrite is used as a sensitizer in photography.
Biological action
Toxic if swallowed, upon receipt of large doses causes irritation, cyanosis, convulsions, death (forms methemoglobin ). Irritating to skin and eyes. The lethal dose of LD50 for rabbits is 200 mg / kg [3] [4] .
The intake of nitrites with food is estimated at 31-185 or 40-100 mg per day [5] .
In drinking water, according to WHO requirements of 1970 and 2004 [6] [7] , the content of nitrites is allowed no more than 44-50 mg per liter [8] .
Acceptable nitrite levels for humans are 3.7 - 7 mg / kg. [eight]
Notes
- ↑ 1 2 Physical quantities: Reference / A. P. Babichev, N. A. Babushkina, A. M. Bratkovsky and others; Ed. I.S. Grigoriev, E.Z. Meilikhova. - M .; Energoatomizdat, 1991 −1232 s - ISBN 5-283-04013-5
- ↑ OPINIONS OF THE SCIENTIFIC COMMITTEE FOR FOOD ON: Nitrates and Nitrite / REPORTS OF THE SCIENTIFIC COMMITTEE FOR FOOD; European Commission, 1997
- ↑ Material Safety Data Sheet Potassium nitrite MSDS # 19480 . Fisher Scientific. 2005
- ↑ http://www.cdc.gov/niosh/ipcsneng/neng1069.html POTASSIUM NITRITE - The National Institute for Occupational Safety and Health (NIOSH), CDC
- ↑ Food sources of nitrates and nitrites: the physiologic context for potential health benefits Am J Clin Nutr July 2009 vol. 90 no. 1 1-10, doi: 10.3945 / ajcn.2008.27131 . "DIETARY NITRATE AND NITRITE INTAKE ESTIMATES"
- ↑ World Health Organization. Recommendations; nitrate and nitrite. In: Guidelines for drinking water quality. 3rd ed. Geneva, Switzerland: WHO, 2004: 417-20.
- ↑ Nitrate and nitrite in drinking-water (WHO / SDE / WSH / 07.01 / 16 / Rev / 1), 2011
- ↑ 1 2 Food sources of nitrates and nitrites: the physiologic context for potential health benefits Am J Clin Nutr July 2009 vol. 90 no. 1 1-10, doi: 10.3945 / ajcn.2008.27131 . POTENTIAL HEALTH RISKS OF EXCESSIVE NITRATE AND NITRITE EXPOSURE
Literature
- Chemistry Handbook / Editorial: Nikolsky B.P. et al. - 2nd ed., rev. - M.-L.: Chemistry, 1966. - T. 1. - 1072 p.
- Chemistry Handbook / Editorial: Nikolsky B.P. et al. - 3rd ed., rev. - L .: Chemistry, 1971. - T. 2. - 1168 p.
- IARC Monographs on the Evaluation of Carcinogenic Risks to Humans VOLUME 94 "Ingested Nitrate and Nitrite, and Cyanobacterial Peptide Toxins", IARC , 2010 ISBN 978-92-832-1294-2 , ISSN 1017-1606