He Potassium nitrite Is a yellowish-white crystalline solid. Its chemical formula is KNO 2 and Has an ionic bond between potassium and one of the nitrite oxides.
Nitrites in general are naturally present in soils, water, animal and plant tissues, and in fertilizers.
Potassium nitrate was first obtained by the Swedish chemist Carl Wilhelm Scheele When he worked in the laboratory of his pharmacy in the town of Köpin. He heated the red potassium nitrate for half an hour until he got what he recognized as a new salt.
The two salts, nitrate and nitrite, were characterized by the French chemist Eugène-Melchior Péligot and the reaction was established as:
This process is still used today for production. Potassium nitrite is obtained from the reduction of potassium nitrate. The production of nitrites is done by the absorption of nitrogen oxides in solutions of potassium hydroxide or potassium carbonate.
However it is not done on a large scale due to the high cost of these bases, in addition to the high solubility of potassium nitrite in water makes recovery difficult. (Potassium Nitrite, s.f.)
Structure of potassium nitrite
Physical and chemical properties
Potassium nitrite is crystalline solid at room temperature, yellowish white. Its molar mass is 85.1 g / mol and its density is 1.915 g / ml. It has a melting point of 441 degrees Celsius and begins to decompose at 350 degrees Celsius. Its boiling point is 537 degrees Celsius at which it explodes.
Potassium nitrite is highly soluble in water. 281 g can be dissolved in 100 ml of water at 0 degrees centigrade, 413 g in 100 ml of water at 100 degrees centigrade. Its solubility at room temperature is 312 g in 100 ml of water. It is also very soluble in ammonia and soluble in hot alcohol.
Reactivity and hazards
Possible explosions
Potassium nitrite is a strong oxidizing agent that can accelerate the combustion of others when there is fire involved. It may react explosively on contact with phosphorus, tin (II) chloride or other strong reducing agents.
Contamination with ammonium compounds may cause spontaneous decomposition. The resulting heat can ignite the combustible material that is present.
Reacts with acids to form toxic fumes of nitrogen dioxide. When mixed with liquid ammonia it forms dipotassium nitrite which is very reactive and explosive. When melted with ammonium salts it leads to violent explosions.
May cause explosions if mixed with potassium cyanide. When small amounts of ammonium sulfate are added to molten potassium nitrate, a vigorous reaction accompanied by a flame (potassium nitrite, 2016) occurs.
Dangerous for the skin
Potassium nitrate is extremely dangerous in case of contact with the skin, eyes, ingestion or inhalation. The severity of the damage will depend on the duration of the contact. Contact with skin may cause irritation, inflammation and abrasion. (Material safety data sheet potassium nitrate, 2013).
Respiratory Hazards
Potassium nitrate can affect breathing. Inhaling the dust can irritate the throat, nose and lungs, causing coughing with phlegm. Higher exposures can cause pulmonary edema, which can eventually lead to death (Pohanish, 2012).
Cardiovascular Conditions
High levels of potassium nitrate can affect the vascular system and interfere with the blood's ability to transport oxygen (methaemoglobinaemia) causing headaches, weakness, dizziness and blue coloration on the skin and mucous membranes known as cyanosis. Higher doses can cause respiratory problems, collapse and even death (Food Additives in Europe 2000, 2002).
Others
Prolonged contact can cause cracked skin, dryness and dermatitis. It can cause lung irritation that can end up in bronchitis. There is also evidence that potassium nitrite can damage developing fetuses.
The toxicity of potassium nitrate is 235 mg per kg of body weight, and studies in rats have shown that there are no effects at doses lower than 10mg KNO2 per kilogram consumed per day (HP Til, 1988) .
Handling and storage
Potassium nitrite is usually stored with other oxidizing agents, and separated from combustible or flammable substances, reducing agents, acids, cyanides, ammonium compounds, amides, and other nitrogen salts in a dry, temperate and well-ventilated place.
It should not be ingested or breathed. In case of insufficient ventilation, the appropriate breathing apparatus, such as mask with anti-gas filter and anti-vapors, should be used. Avoid contact with skin and eyes.
If swallowed, seek medical advice immediately. It is advisable, for these cases, to show the container bottle or the product label. Always wear a lab coat, safety glasses and latex gloves to prevent accidents. (Material safety data sheet potassium nitrate, 2013)
Medical Uses
The medical interest of inorganic nitrites began to boom when their efficacy was observed in the treatment of angina. Previously, the treatment for said evil was done by venesection. Having the wrong belief that the pain was due to high blood pressure, the veins were cut and the patient was allowed to bleed. Needless to say, such treatment was inconvenient.
It was in the 1860s that the doctor Thomas Lauder Brunton Decided to test in patients with angina pectoris the inhalation of amyl nitrite, a compound that by date had recently been synthesized by one of his colleagues and had been shown to lower blood pressure in animals.
The results in his patients were fruitful. The pain associated with this condition diminished rapidly and the effect lasted for several minutes, long enough for the patient to recover and rest.
For a long time, amyl nitrite was the treatment chosen for angina pectoris, but because of its volatility, it was replaced by salts such as potassium nitrite, which had the same effect (Butler & Feelisch, 2008).
In healthy human volunteers, the effect of potassium nitrite on nervous system , spinal cord , brain , Pulse, blood pressure and respiration as well as their variability in the different individuals.
The most important observation was that even in small doses of approximately 30 mg, given orally, causes at first an increase in blood pressure; Followed by a moderate decrease. At higher doses, pronounced hypotension occurred.
They also observed that potassium nitrite, regardless of how it is administered, had a profound effect on the appearance and oxygen carrying capacity of blood. They compared the biological action of potassium nitrite with that of amyl and ethyl nitrites and concluded that the similarity of action depends on the conversion of organic nitrites to nitrous acid.
Under conditions of hypoxia, nitrite can release nitric oxide, which causes potent vasodilation. Several mechanisms have been described for the conversion of nitrite to NO, including the enzymatic reduction by xanthine oxidoreductase, nitrite reductase and NO synthase (NOS), as well as non-enzymatic dismutation reactions. (Albert L. Lehninger, 2005).
Generally, in pharmacology, potassium salts, rather than sodium salts, are used to treat patients with hypertension.
Other uses
Among other uses given to potassium nitrate, as well as sodium nitrate, is the preservation of foods, particularly cured meats such as bacon and chorizo. Sodium and potassium nitrite are used as antimicrobial preservatives to prevent degradation of such foods by bacteria.
The detailed mechanism of these chemical compounds ranges from inhibiting the growth of bacteria to inhibiting specific enzymes.
Sodium nitrite is used for curing meat, not only because it prevents bacterial growth, but also as an oxidizing agent; In a reaction with the myoglobin of meat, gives the product a desirable pink-red"pink"color.
This use of nitrite dates back to the Middle Ages and in the United States has been formally used since 1925. Because of the relatively high toxicity of nitrite, the concentration of nitrite in meat products is 200 ppm, which is the maximum allowable concentration .
At these levels, between 80 and 90% of the nitrite in the average US diet does not come from cured meat products, but from the natural production of nitrite from the intake of vegetable nitrate.
Under certain conditions (especially during cooking) the nitrites in the meat may react with amino acid degradation products, forming nitrosamines, which are known carcinogens.
However, the role of nitrites (and to some extent nitrates) in preventing botulism by preventing the germination of C. botulinum endospores has prevented the complete elimination of nitrites from cured meat in the US. UU.
The meat can not be considered cured without the addition of nitrites. They are considered irreplaceable in preventing Botulinum Of the consumption of dried cured sausages, such as sausage or sausage, preventing germination of the spore. In mice, foods rich in nitrites along with unsaturated fats can prevent hypertension, which is an explanation of the apparent effect on the health of the Mediterranean diet (Nathan S. Bryan, 2011).
Other uses given to potassium nitrite are in the manufacture of heat transfer salts, corrosion inhibitor and antifouling agent, as a reagent for reduction oxide reactions, as an additive in paints and coatings and for the treatment of water (Potassium Nitrite, sf).
Biochemistry
Nitrates and nitrites given orally are absorbed and transferred to the blood in the upper part of the gastrointestinal tract. Foods abundant in pectin may delay the absorption that may occur further down the intestine, with a possible increased risk of microbial transformation of nitrate into nitrite.
Irrespective of the route of exposure, nitrate and nitrite are rapidly transferred into the blood. Nitrite is gradually oxidized to nitrate which is easily distributed in most body fluids (urine, saliva, gastric juice, sweat, ileostomy fluid). Nitrate does not accumulate in the body.
The main mechanism of nitrite toxicity is the oxidation of ferrous iron (Fe2 +) in deoxyhemoglobin to the ferric valence state (Fe3 +), producing methemoglobin. Methemoglobin can not bind or transport reversibly circulating oxygen.
Depending on the percentage of total methemoglobin in oxidized form, the clinical picture is one of oxygen deficiency with cyanosis, cardiac arrhythmias and circulatory failure, and progressive effects on the central nervous system (CNS). Effects on CNS can range from mild dizziness and lethargy to coma and seizures (Potassium Nitrite, s.f.).
The main concern of the possible long-term effects of exposure to nitrate and nitrite is associated with the formation of nitrous compounds, many of which are carcinogenic. This formation can take place wherever nitrite and nitrosable compounds are present, but it is favored by acidic conditions or the presence of some bacteria.
The gastrointestinal tract and especially the stomach are considered as the main site of formation, but the nitrosation reactions can also take place in an infected urinary bladder
Urinary and fecal excretion of nitrite is very low, since most of the nitrite entering the bloodstream or through the gastrointestinal tract (GI) is rapidly converted to nitrate, bound to GI content, or reduced by enteric bacteria.
The rapid decrease in nitrite blood concentrations is attributed to nitrite reactivity with hemoglobin and other endogenous compounds, a hypothesis supported by increased nitrate concentration following intravenous nitrite administration in rats.
References
- Albert L. Lehninger, D.L. (2005). Lehninger Principles of Biochemistry. W. H. Freeman.
- Butler, A., & Feelisch, M. (2008). Therapeutic Uses of Inorganic Nitrite and Nitrate. Journal of the American Heart Association, 2151-2159. Excerpted from circ.ahajournals.org.
- Food Additives in Europe 2000. (2002). Copenaghen: nord theme.
- . Til, H. F. (1988). Evaluation of the oral toxicity of potassium nitrite in a 13-week drinking-water study in rats. Food and Chemical Toxicology Volume 26, Issue 10, 851-859. Sciencedirect.com.
- Material safety data sheet potassium nitrate. (2013, May 21). Retrieved from science lab: sciencelab.com.
- Nathan S. Bryan, J.L. (2011). Nitrite and Nitrate in Human Health and Disease. Human press.
- Pohanish, R. P. (2012). Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Volume 1 sixth edition. Elsevier.
- Potassium nitrite. (2016). Retrieved from cameo chemical: cameochemicals.noaa.gov.
- Potassium Nitrite. (S.f.). Retrieved from Pub Chem open chemistry database: pubchem.ncbi.nlm.nih.gov.
- Royal society of chemistry. (2015). Potassium nitrite. Retrieved from chemspider: chemspider.com.