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You may have encountered some salts of ternary acids without even being aware of them. For example, did you know that cigarette paper and tobacco are treated with potassium nitrate, KNO3, so that smokers do not have to relight their cigarettes as often as cigar and pipe smokers do? When heated by a burning cigarette, potassium nitrate slowly decomposes into potassium nitrite (KNO2) and oxygen (O2). This oxygen supports combustion and keeps cigarettes from becoming extinguished. Unfortunately, the luxury of having cigarettes remaining lighted comes at a high price. When people fall asleep while smoking cigarettes in bed, house fires often result. Cigarettes are the leading cause of home fires in this country.
Turning to your pantry, the iron in many of your breakfast cereals and breads may have been added in the form of iron(II) sulfate, FeSO4, or iron(II) phosphate, Fe3(PO4)2. Fruits and vegetables keep fresh longer after an application of sodium sulfite, Na2SO3, and sodium hydrogen sulfite, NaHSO3. The red color of fresh meat is maintained for much longer by the additives sodium nitrate, NaNO3, and sodium nitrite, NaNO2.
Fruits keep fresh longer after an application of
sodium sulfite. (V. Holtgrewe)
Other salts of ternary acids that you may find in your home include potassium chlorate, KClO3, in matches as an oxidizing agent and oxygen source; sodium hypochlorite, NaClO, in bleaches and mildew removers; and ammonium carbonate, (NH4)2CO3, which is the primary ingredient in smelling salts. Fireworks get their brilliant colors from salts such as barium nitrate, Ba(NO3)2, which imparts a green color; strontium carbonate, SrCO3, which gives a red color; and copper(II) sulfate, CuSO4, which produces a blue color. Should your fireworks get out of hand and accidentally start a fire, the ammonium phosphate, (NH4)3PO4, sodium hydrogen carbonate, NaHCO3, and potassium hydrogen carbonate, KHCO3, in your ABC dry fire extinguisher will come in handy.
Whitten/Davis/Peck: General Chemistry with Qualitative Analysis, 5/e, p.349