Potassium nitrate is represented by KNO3. It is a major source of nitrogen and is commonly known as saltpetre. Potassium nitrate is a orthorhombic crystal structure at room temperature, then changes to trigonal state at higher temperature. It is highly soluble in water and as temperature increases, solubility increases. It is insoluble in alcohol and is not poisonous; it can react explosively with reducing agents, but it is not explosive on its own.
In earlier times, potassium nitrate was obtained from natural mineral sources and from caves. Nowadays the production of potassium nitrate is done by making ammonium nitrate react with potassium hydroxide.
NH4NO3 (aq) + KOH (aq) → NH3 (g) + KNO3 (aq) + H2O (l)
For industrial scale, sodium nitrate and potassium chloride are reacted together to produce potassium nitrate and sodium chloride.
NaNO3 (aq) + KCl (aq) → NaCl (aq) + KNO3 (aq)
Potassium nitrate is widely used for salting meats worldwide. It is also used as thickening agent in soups and stews. It is added to cooking foods to reduce their cooking time of beans and cooking meat.
Potassium nitrate is a major source of both nitrogen and potassium. They are 2 of the most important macronutrients required for soil being fertile and for plant growth. Hence they are added to fertilizers.
Potassium nitrate is added to black powder in explosives and gives a smokeless powder. Potassium nitrate is added in toothpastes for sensitive teeth. It is widely used in the field of electrochemistry.