Prague powder #1 or pink salt contains 93.75% table salt

Salt

In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

 and 6.25% sodium nitrite

Sodium nitrite

Sodium nitrite is the inorganic compound with the chemical formula NaNO2. It is a white to slight yellowish crystalline powder that is very soluble in water and is hygroscopic...

. Prague powder #2 contains sodium nitrate in addition to sodium nitrite. Both kinds are used in the preserving and curing of meats, and in sausage

Sausage

A sausage is a food usually made from ground meat , mixed with salt, herbs, and other spices, although vegetarian sausages are available. The word sausage is derived from Old French saussiche, from the Latin word salsus, meaning salted.Typically, a sausage is formed in a casing traditionally made...

 making. As an additive, the sodium nitrite or nitrate serves to inhibit the growth of bacteria, specifically Clostridium botulinum

Clostridium botulinum

Clostridium botulinum is a Gram-positive, rod-shaped bacterium that produces several toxins. The best known are its neurotoxins, subdivided in types A-G, that cause the flaccid muscular paralysis seen in botulism. It is also the main paralytic agent in botox. C. botulinum is an anaerobic...

in an effort to prevent botulism

Botulism

Botulism also known as botulinus intoxication is a rare but serious paralytic illness caused by botulinum toxin which is metabolic waste produced under anaerobic conditions by the bacterium Clostridium botulinum, and affecting a wide range of mammals, birds and fish...

, and helps preserve the color of cured meat. Curing salt may be dyed pink, helping it blend better with meat, and moreover preventing it from being confused for and consumed as common table salt.