Tetrasodium pyrophosphate, which does
not sequester calcium as the higher phos-
phates, is very stable above 60ºC in alkaline
solutions.
Sodium tripolyphosphate and sodium
tetraphosphate have calcium-sequestering
power superior to that of tetrasodium
pyrophosphate but tend to revert to
orthophosphate and pyrophosphate when
held above 60ºC or in the alkalinity of pH 10
or higher.Sodium hexametaphosphate(Cal-
gon) is an effective calcium sequestrant with
limited magnesium-sequestering power.
Amorphous phosphates are complex glassy
phosphates with excellent calcium-sequester-
ing power.
Organic chelating agents, which are used
in formulation in water conditioners, are
more efficient than are phosphates in seques-
tering calcium and magnesium ions and in
minimizing scale buildup. Most organic
agents are salts of ethylenediaminetetraacetic
acid (EDTA). The chelating agents are sta-
ble above 60ºC in solution for extended peri-
ods of storage. These chelating properties
for EDTA salts improve as pH increases.
They may be used in conveyor lubricant
formulations.
Surfactants
These surface-active agents function to
facilitate the transport of cleaning and sani-
tizing compounds over the surface to be
cleaned. Surfactants are known to “make the
water wetter”. Although the major functions
of surfactants are wetting and penetrating,
detergency characteristics, such as emulsifi-
cation, deflocculation, and suspension of
particles, contribute to their effectiveness.
Surfactants are classified as synthetic
detergents because of their numerous prop-
erties. As auxiliaries, they are also classified
in the same three groups, according to their
wetting properties and active components in
solution. These auxiliaries are classified as
cationic surfactants, which ionize in solution
to produce active positively charged ions and
serve as excellent bactericidal agents and
ineffective detergents; anionic surfactants,
which ionize in solution to produce active
negatively charged ions and are generally
excellent detergents and ineffective bacteri-
cides; and nonionic surfactants with no pos-
itive and negative ions in solution or
bactericidal properties but with excellent
wetting and penetrating characteristics. In
addition, the amphotericsurfactants have a
positive or negative charge, depending on the
pH of the solution.
The general structure for anionic surfac-
tants is Q–X−M+, where Q is the hydropho-
bic portion of the molecule, X−is the anionic
or hydrophilic portion, and M+is the coun-
terion in solution. The hydrophobic portion
of the molecule is normally a hydrocarbon
chain of the form CnH2n+ 1 , which is usually
designated as R. Q may represent an alkyl-
substituted aromatic molecule, amide, ether,
fatty acid, oxyethylated alcohol, phenol,
amine, or olefin. The two most familiar
anionic surfactants are soaps and linear
alkylbenzene sulfonates.
The hydrophobic group forms a part of
the cation dissolved in water in the cationic
surfactants, whereas the hydrophobic por-
tion of an anionic surfactant forms a part of
the anion in aqueous solution. A cationic
compound is formed by reacting a tertiary
amine with an alkyl halide to form a quater-
nary ammonium salt R 1 R 2 R 3 +R4XfR 1
R 2 R 3 R 4 N++X−. At least one of the Rsub-
stituents is a hydrophobic group, such as
dimethylammonium chloride, a germicidal
agent.
The hydrophilic portion of nonionic sur-
factants often is composed of one or more
condensed blocks of ethylene oxide. The
hydrophobic portion can be any of several
groups, including those named for the anionic
types. The bond between the hydrophobe and
the hydrophile may be an ether grouping or
an amide or ester grouping. Other nonionicCleaning Compounds 155