necessary because this acid can react
with hard-water constituents to form
calcium oxalate, a poisonous precipitate.
●Citric acid, which does not produce
toxic compounds but is not as efficient
as oxalic acid in rust removal.
●Gluconic acid, which removes alkali and
protein films through sequestering
power without a toxic effect and may be
used as a water conditioner.
●Sodium bisulfate, a low-cost course for
heavy-duty powdered acid cleaners.Protective Colloids and Suspending Agents
Hydrophilic colloids that prevent particle
redeposition on the cleaned surface are com-
monly referred to as protective colloids, thick-
eners, and suspending agents. Examples are
gelatin, glue, starch, sodium cellulose sulfate,
hydroxyethyl cellulose, and carboxymethyl
cellulose. Other agents with protective proper-
ties are:
●Low-alkali, high-silica compounds, such
as glassy or colloidal silicates, metasili-
cates, and sodium chromates (and gela-
tin), which inhibit tin and aluminum
spangling.
●Sodium chromate or dichromate, borax,
and sodium nitrate in neutral detergent
systems, which are efficient inhibitors of
steel and iron corrosion.
●Metasilicates and colloidal silicates,
which protect glass and enamel surfaces
from caustic etching.
●Sodium sulfite, sodium fluorosilicate, and
metabisulfite, which are reducing agents
in the detergent system and protect tin
and tin-plated surfaces by removing dis-
solved oxygen from the wash solution.Cleaning auxiliaries
Various auxiliaries protect sensitive sur-
faces or improve the cleaning properties of a
compound. Some are described below.
Sequestrants
These auxiliaries, also called chelating
agents and sequestering agents, chelate by
complexing with magnesium and calcium
ions to produce compounds. This action
effectively reduces the reactivity of water
hardness constituents. Sequestrants consist of
polyphosphates or organic amine derivatives.
Phosphates differ in heat stability, wetting,
and rinsing properties, water conditioning,
hardness, and sequestering power.
Cleaning detergents consist of a surfac-
tant and a builder. Builders increase the
effectiveness of a cleaner by controlling
properties of the cleaning solution that tend
to reduce the surfactant’s effectiveness. Phos-
phates are considered excellent builders,
especially for heavy-duty cleaning com-
pounds. Phosphates serve as builders in
cleaning compounds by providing:
●Enhancement of the wetting effect and
resultant cleaning efficiency of cleaning
compounds.
●Sufficient alkalinity necessary for effec-
tive cleaning without being hazardous.
●Maintenance of the proper alkalinity in
the cleaning solution through buffering
ability.
●Emulsification of oily, greasy soil by
degradation and subsequent release
from the surface to be cleaned.
●Loosening and suspension of soil with
the ability to prevent redeposition on
the clean surface.
●Water softening by keeping minerals
dissolved to prevent settling on what is
being cleaned.
●Reduction in numbers of bacteria asso-
ciated with a clean surface.There are a number of polyphosphates
of special significance.Sodium acid pyropho-
sphate has excellent buffering and peptiz-
ing properties, with limited capability for
sequestering water hardness constituents.