NaNO 2 and NaNO 3 as Food Additives
The brown color of “old” meat is the result of oxidation of blood and is objectionable to
many consumers. Nitrites and nitrates are added to food to retard this oxidation and also
to prevent growth of botulism bacteria. Nitrate ions, NO 3 , are reduced to NO 2 ions,
which are then converted to NO. This in turn reacts with the brown oxidized form of the
heme in blood. This reaction keeps meat red longer. Controversy has arisen, however,
concerning the possibility that nitrites combine with amines under the acidic conditions
in the stomach to produce carcinogenic nitrosoamines.PHOSPHORUS
Phosphorus is always combined in nature. Phosphorus is present in all living organ-
isms—as organophosphates and in calcium phosphates such as hydroxyapatite,
Ca 5 (PO 4 ) 3 (OH), and fluorapatite, Ca 5 (PO 4 ) 3 F, in bones and teeth. It also occurs in these
and related compounds in phosphate minerals, which are mined mostly in Florida and
North Africa.
Industrially, the element is obtained from phosphate minerals by heating them at 1200
to 1500°C in an electric arc furnace with sand (SiO 2 ) and coke.24-17
RRNNO (R and R organic groups)
nitroso
group
amine
group964 CHAPTER 24: Some Nonmetals and Metalloids
Nitric acid, HNO 3 , reacts with protein-containing materials such as this feather, staining
them yellow. Perhaps you have spilled nitric acid on your skin and seen it turn yellow.
Copper (left beaker) and zinc (right
beaker) react with concentrated nitric
acid.White phosphorus reacts with air, so
it is stored under water. It contains
tetrahedral P 4 molecules.