Description
SULFAMIC
ACID
Sulfamic acid is a moderately strong acid. Because the
solid is non-hygroscopic, it is used as a standard in acidimetry
(quantitative assays of acid content).
Sulfamic acid melts at **5 °C before decomposing
at higher temperatures to H2O, SO3, SO2, and
N2.
Water solutions are unstable and slowly hydrolyze
to ammonium bisulfate, but the crystalline solid is indefinitely
stable under ordinary storage conditions.
Sulfamic acid is used as an acidic cleaning agent,
sometimes pure or as a component of proprietary mixtures, typically
for metals and ceramics. It is frequently used for removing rust
and limescale, replacing the more volatile and irritating
hydrochloric acid, which is however cheaper. It is often a
component of household descaling agents, for example, Lime-A-Way
Thick Gel contains up to 8% sulfamic acid and pH 2 - 2.2, or
detergents used for removal of limescale. When compared to most of
the common strong mineral acids, Sulfamic acid has desirable water
descaling properties, low volatility, low toxicity and is a water
soluble solid forming soluble calcium and iron-III salts. Its also
finds applications in the industrial cleaning of dairy and
brew-house equipment. Although it is considered less corrosive than
hydrochloric acid due to its lower pKa, corrosion inhibitors are
often added to commercial cleansers of which it is a component. It
is possible that the amino group could act as a ligand under
certain circumstances, as does the chloride ion for Fe-III, when
hydrochloric acid is used in rust removal.
