Potassium nitrate is not used:

Correct option is D

The correct answer is (d) as a preservative of meat products.
Potassium nitrate (KNO₃), also known as saltpeter, is used in several applications:
Fertilizer: It is commonly used in fertilizers due to its potassium and nitrogen content, essential for plant growth.
Medicine: Potassium nitrate has historically been used in medicine, particularly in treating conditions like asthma and bronchitis, and is also found in toothpaste for sensitive teeth.
Gunpowder: It is a key component of gunpowder (black powder), used in fireworks and explosives.
However, it is not commonly used as a preservative for meat products today, despite its historical use for this purpose. It has largely been replaced by other nitrates and nitrites in modern food preservation practices due to health concerns.
Information Booster: ● Potassium nitrate is a key ingredient in fertilizers due to its high nitrogen content, essential for plant growth. ● It is a crucial component of gunpowder, where it provides oxygen to enhance combustion. ● Historically, potassium nitrate was used in curing meats, such as ham, to inhibit bacterial growth and enhance preservation. ● While it had historical medical uses, such as treating asthma, these uses are no longer prevalent, as modern medicine provides better alternatives. ● Potassium nitrate has applications in industries beyond agriculture and food, such as pyrotechnics and ceramics. ● The compound also appears in some formulations of toothpaste to reduce tooth sensitivity, though this is not a primary medicinal application.