The Potassium nitrite . It is the inorganic compound with the chemical formula KNO 2 . It is an ionic salt of potassium ions K ions and nitrite NO 2 – , which forms a white or slightly yellow crystalline, hygroscopic powder that is soluble in water .
Summary
[ hide ]
- 1 Origin
- 1 Obtaining
- 2 Chemical Reactions
- 3 Medical uses
- 4 Applications
- 1 Reactivity hazards
- 2 Storage requirements
- 5 External links
- 6 Sources
Origin
Nitrite is present at trace levels in soils, natural waters, plant and animal tissues, and fertilizers. The pure form of nitrite was first made by the prolific Swedish chemist Scheele working in the laboratory of his pharmacy in the Kping market area. Potassium nitrate is heated red hot for half an hour and what he recognized as a new “salt” is obtained. The two compounds are characterized by Pligot and the reaction was stated as:
2KNO 3 = 2KNO 2 O 2 .
Obtaining
Potassium nitrite can be obtained by reducing potassium nitrate. The production of potassium nitrite by absorption of nitrogen oxides into potassium hydroxide or potassium carbonate is not used on a large scale due to the high price of these alkalis. Furthermore, the fact that potassium nitrite is highly soluble in water makes the solid difficult to recover.
Chemical reactions
The mixture of cyanamide and KNO2 produces changes from white solids to liquid yellow and then to orange solid, forming cyanogen and ammonia gases. No external energy is used and the reactions are carried out with a small amount of O 2 .
Potassium nitrite forms potassium nitrate when heated in the presence of oxygen 550-790. The reaction rate increases with temperature, but the extent of the reaction decreases. At 550 and 600 the reaction is continuous and eventually reaches completion. From 650 to 750, as is the case for potassium nitrate decomposition, the system reaches equilibrium. At 790, a rapid decrease in volume is observed first, followed by a 15 minute period during which no volume changes occur. This is followed by an increase in volume mainly due to the evolution of nitrogen, which is attributed to the decomposition of potassium nitrite.
Potassium nitrite reacts at an extremely slow rate with a liquid ammonia solution of potassium amide at room temperature, and in the presence of ferric oxide or cobalt oxide, to form nitrogen and potassium hydroxide.
Medical uses
Interest in a medical paper for inorganic nitrite was first sparked by the spectacular success of organic nitrites and related compounds in the treatment of angina pectoris. While working with butter at the Royal Infirmary in Edinburgh in 1860, Brunton pointed out that the pain of angina can be lessened by bleeding and wrongly concluded that the pain must be due to elevated blood pressure. As a treatment for angina pectoris, reducing blood flow by venous dissection was inconvenient. Therefore, he decided to test the effect on a patient of inhaling amyl nitrite, a recently synthesized compound that his colleague had shown to have lower blood pressure in animals. The pain associated with an angina attack quickly disappeared, and the effect lasted for several minutes, usually long enough for the patient to recover by resting. For a time, amyl nitrite was the preferred treatment for angina pectoris, but due to its volatility, it was replaced by chemically related compounds that had the same effect.
The effect of potassium nitrite on the nervous system, brain, spinal cord, pulse, arterial blood pressure, and respiration of healthy human volunteers, as well as variability between individuals. The most important observation was that even a small dose of <0.5 grains administered orally caused, first, an increase in arterial blood pressure, followed by a moderate decrease. With larger doses, pronounced hypotension occurred. They also observed that potassium nitrite, however administered, had a profound effect on the appearance and oxygen-carrying capacity of the blood. They compared the biological action of potassium nitrite with that of amyl and ethyl nitrites and came to the conclusion, rather interestingly,
Acidified nitrite solutions have been used successfully to generate NO and to induce vascular relaxation in blood vessels in isolated studies, and the same reaction mechanism has been proposed to explain the biological action of nitrite.
Applications
Potassium nitrite is used in the manufacture of heat transfer salts. As an E 249 food additive, potassium nitrite is a preservative similar to sodium nitrite and is approved for use in the EU, US, Australia and New Zealand .
Reactivity hazards
When reacted with acids, potassium nitrite forms toxic nitrous oxides. Fusion with ammonium salts results in effervescence and ignition. Reactions with reducing agents can cause fires and explosions.
Storage requirements
Potassium nitrite is stored with other oxidizing agents, but separated from flammable materials, fuels, reducing agents, acids, cyanides, ammonium compounds, amides, and other nitrogenous salts in a cool, dry, and well-ventilated place
