Potassium nitrate is not used:

The correct answer is  as a preservative of meat products.

Key PointsPotassium Nitrate Uses

• As a Fertilizer: Potassium nitrate is a major component in fertilizers. It provides essential nutrients like potassium and nitrogen, which are crucial for plant growth and development. Hence, statement 1 is correct.
• In Medicine: Potassium nitrate has applications in the medical field, particularly in treating certain conditions like asthma and as a diuretic. It is also found in some toothpaste formulations to reduce tooth sensitivity. Hence, statement 2 is correct.
• In Making Gunpowder: Potassium nitrate is a key ingredient in gunpowder, along with charcoal and sulfur. It acts as an oxidizer, which is essential for the combustion process. Hence, statement 3 is correct.
• As a Preservative of Meat Products: Potassium nitrate is not typically used as a preservative for meat products. Instead, sodium nitrate or sodium nitrite is commonly used for this purpose due to their better preservation properties and ability to inhibit bacterial growth. Hence, statement 4 is incorrect.

Additional Information

• Potassium Nitrate in Agriculture: It is extensively used in agriculture as a source of nitrogen and potassium, which are two of the three primary nutrients essential for plant growth. Its water-soluble nature makes it ideal for use in fertigation systems.
• Medical Applications: Beyond its use in treating asthma and as a diuretic, potassium nitrate is used in some dental products to alleviate tooth sensitivity. It works by blocking the tubules in the dentin that lead to the nerves, thereby reducing pain.
• Gunpowder Composition: The traditional composition of gunpowder, also known as black powder, consists of 75% potassium nitrate, 15% charcoal, and 10% sulfur. The potassium nitrate acts as an oxidizer, the charcoal serves as the fuel, and the sulfur lowers the ignition temperature and increases the speed of combustion.
• Preservation of Meat Products: Sodium nitrate and sodium nitrite are more commonly used for preserving meat products. These compounds help to maintain the red color of meat and prevent bacterial growth, particularly Clostridium botulinum, which causes botulism.